Speroff’s Clinical Gynecologic Endocrinology and Infertility - Book 4

REGULATION OF TESTICULAR FUNCTION

The testes have two distinct components, the seminiferous tubules (the site of
spermatogenesis) and the Leydig cells (the source of testosterone). The seminiferous
tubules are composed of germ cells, called spermatogonia, and Sertoli cells, which
produce inhibin. Tight junctions between the Sertoli cells form a diffusion barrier
known as the blood-testis barrier (similar to the blood-brain barrier), which protects
the germ cells from antigens, antibodies, and environmental toxins.2 The seminiferous
tubules are therefore essentially avascular, so regulatory molecules must enter by
diffusion. The Leydig cells are located in the connective tissue between the
seminiferous tubules.

Spermatogenesis

After migration of the germ cells to the genital ridge during embryogenesis, there are
approximately 300,000 spermatogonia in each gonad. Each undergoes a series of
mitotic divisions, and by puberty, there are about 600 million in each testis. Continued
proliferation during adult life supports the production of approximately 100–200
million sperms each day and more than 1 trillion during a normal reproductive
lifespan.3 A spermatogonia-specific transcription factor identified in mice, Plzf, is
required for maintenance of the spermatogonial stem cell pool.4,5

As spermatogenesis begins, the diploid (46 chromosomes) spermatogonia grow to
become primary spermatocytes before entering meiosis. The first meiotic division
yields 2 haploid (23 chromosomes, each made up of 2 chromatids joined at the
centromere) secondary spermatocytes, each of which gives rise to 2 spermatids (23
chromosomes, each consisting of a single chromatid) during the second meiotic
division. Thereafter, each spermatid gradually matures to become a mature
spermatozoon. Approximately 3 million spermatogonia begin development each day, but
about half of all potential sperm production is lost during meiosis (Figure 26.1).6

FIGURE 26.1

As spermatids develop into mature sperms, the nucleus moves to an eccentric position
at the head of the spermatid and becomes covered by an acrosomal cap.7 The core of the
sperm tail consists of nine outer fibers around two inner fibers, surrounded in the
middle section by mitochondria. The tail fibers are attached to each other by arms

containing the protein dynein, which is an ATPase. Hydrolysis of ATP (adenosine
triphosphate) in the adjacent mitochondria provides the energy for sperm motility, which
is accomplished by a sliding action between the fibers in the sperm tail.

The spermatogenic process is directed by genes located on the Y chromosome8
and takes approximately 70 days to complete from the spermatocyte stage.9
Another 12–21 days are required for the transport of sperms from the testis
through the epididymis to the ejaculatory duct.10 During passage through the
epididymis, sperms mature further to develop the capacity for sustained motility.11 The
long time required for sperm development and transit implies that the results of a
semen analysis reflect conditions existing many weeks earlier. Final maturation, or
capacitation, of sperms may occur after ejaculation into the female genital tract. Normal
spermatogenesis requires the lower temperature of the scrotum, but slight increases in
scrotal temperature, such as those associated with the wearing of athletic supporters, do
not appear to have any measureable adverse effect.12 Semen includes secretions
contributed by the prostate, the seminal vesicles, and the distal vasa deferentia.

Hormone Regulation

Normal testicular function requires the actions of both pituitary gonadotropins, follicle-
stimulating hormone (FSH) and luteinizing hormone (LH). LH stimulates the Leydig
cells in the testicular interstitium to synthesize and secrete testosterone (approximately
5–10 mg/day). The actions of LH are supported indirectly by FSH, which induces the
appearance of LH receptors on testicular Leydig cells13 and stimulates synthesis of
androgen-binding protein (ABP) in Sertoli cells.14 Testosterone is secreted both into the
circulation and into the lumen of the seminiferous tubules where it is highly concentrated
to the levels needed to support spermatogenesis in the germinal epithelium and sperm
maturation in the epididymis; concentrations within the testes are 50–100 times higher
than in blood.15,16 The actions of testosterone in support of spermatogenesis are
mediated by the Sertoli cells, which line the seminiferous tubules and contain androgen
receptors.16

Rising serum testosterone levels exert feedback inhibition on LH secretion, acting
both at the hypothalamic level to slow the pulsatile release of hypothalamic
gonadotropin-releasing hormone (GnRH),17,18 probably via a mechanism involving
endogenous opiates,19 and at the pituitary level to decrease pituitary gonadotrope
sensitivity to GnRH stimulation.20 Numerous studies involving infusions of testosterone,
estradiol, or dihydrotestosterone (which cannot be converted to estrogen) or the
administration of estrogen antagonists in normal subjects,21,22 in individuals with
androgen insensitivity,23 and in men with idiopathic hypogonadotropic hypogonadism24
have established that testosterone exerts its negative feedback effects on LH secretion
both directly and indirectly via conversion to estradiol in the brain. Evidence that
estradiol is involved in LH feedback control derives from the observation that LH
levels are elevated in men with aromatase deficiency25 and after treatment with
aromatase inhibitors.26

In contrast to its effects on LH secretion, physiologic levels of testosterone do not
suppress FSH secretion. Rather, the regulation of pituitary FSH (but not LH) secretion is
controlled by inhibin. FSH levels rise progressively after orchiectomy, the observation
that led ultimately to the discovery of inhibin. Inhibin B is synthesized and secreted by
Sertoli cells in response to FSH stimulation and specifically inhibits GnRH-stimulated
pituitary FSH secretion.27,28,29 In the castrated male monkey, treatment with recombinant
human inhibin can restore normal FSH levels in the absence of testosterone.30 Sertoli
cell inhibin B secretion is modulated indirectly by LH via testosterone, which inhibits
Sertoli cell inhibin B gene expression.31 Inhibin A is not produced in any significant
amount in men. Evidence from studies in vitro suggests that other autocrine/paracrine

regulatory mechanisms involving locally produced growth factors, neuropeptides,
vasoactive peptides, and immune-derived cytokines also are involved, much like the
complex interactions that operate in the ovarian follicle.32,33,34,35,36 The Sertoli cells of
the testis are analogous to the granulosa cells of the ovary, and the Leydig cells are
comparable to the theca cells.

The extent to which FSH and LH are needed to initiate and maintain
spermatogenesis has been difficult to define because observations in various natural and
experimentally induced conditions have yielded conflicting evidence. The presence of
sperms in the ejaculate of a man with an inactivating mutation in the LH β-subunit gene
and in other men with isolated LH deficiency suggests that FSH alone can initiate
spermatogenesis,37 although the possibility of some residual LH activity or FSH-
stimulated Leydig cell testosterone production via Sertoli cell factors cannot be
excluded.38 Conversely, low-level sperm production in men with inactivating mutations
of the FSH receptor39 and other forms of isolated FSH deficiency40,41 suggest that LH-
driven testosterone production alone can initiate spermatogenesis, although the
possibility of residual FSH activity in the presence of high circulating FSH
concentrations must be acknowledged. Evidence that high doses of exogenous
testosterone can stimulate complete spermatogenesis in immature monkeys, albeit at low
levels, further suggests that FSH is not an absolute requirement,42 but descriptions of
azoospermic men with mutations in the FSH β-subunit gene suggest the opposite.43,44 In
men with hypogonadotropic hypogonadism of prepubertal onset, normal
spermatogenesis can be stimulated by combined treatment with human chorionic
gonadotropins (hCG, having potent LH-like actions) and human menopausal
gonadotropin (containing FSH), but not by treatment with hCG alone45 (Figure 26.2).

FIGURE 26.2

The requirements for the maintenance of spermatogenesis are similarly controversial.
The observation in monkeys that exogenous FSH can maintain testicular volume and the
numbers of spermatogonia after complete suppression of gonadotropin secretion by
treatment with a GnRH antagonist suggests that FSH alone can maintain spermatogenesis
in primates, at least to some degree.46,47 The description of a unique individual with an
activating mutation of the FSH receptor (function in the absence of FSH stimulation) and
normal inhibin B levels (a marker for FSH-stimulated Sertoli cell function)48 who had
undergone hypophysectomy for removal of a benign pituitary tumor (eliminating all
endogenous gonadotropin secretion) and remained fertile while receiving only
physiologic exogenous testosterone replacement therapy (normally inadequate to
support spermatogenesis in hypophysectomized men) serves to further illustrate the

importance of FSH in maintaining spermatogenesis.49 In contrast, the restoration of
fertility after treatment with only exogenous hCG in azoospermic men with isolated
gonadotropin deficiency (low levels of both FSH and LH) suggests that although LH-
stimulated testosterone production may be insufficient to initiate spermatogenesis, it is
sufficient to maintain spermatogenesis.50 In men who develop hypogonadotropic
hypogonadism after puberty, during adulthood (e.g., due to a pituitary tumor),
spermatogenesis stops but usually can be restored by treatment with hCG alone.45

Regardless whether FSH- or LH-stimulated testosterone alone is sufficient to
initiate or to maintain spermatogenesis, both clearly are required for qualitatively
and quantitatively normal sperm production. The importance of FSH has been
demonstrated in a variety of experiments in nonhuman primates and men involving the
selective suppression of FSH by immunization against FSH or by high-dose chronic
exogenous hCG treatment. FSH suppression induces both qualitative and quantitative
abnormalities of semen quality that can be reversed by simultaneous treatment with
exogenous FSH but not with testosterone.51,52,53,54,55 Moreover, in male contraceptive
trials involving treatment with high doses of testosterone, alone or in combination with
levonorgestrel to suppress spermatogenesis, azoospermia developed only in men whose
serum FSH concentration was suppressed to undetectable levels.56,57 The importance of
testosterone in spermatogenesis is evident from observations that FSH alone can induce
proliferation of the seminiferous epithelium in prepubertal monkeys, but only treatment
with both FSH and hCG increases testicular volume and the numbers of Sertoli cells
and spermatogonia.58,59 Also, in men with idiopathic hypogonadotropic hypogonadism
(due to absent GnRH stimulation), exogenous pulsatile GnRH stimulation or a
combination of exogenous FSH and LH or hCG can induce spermatogenesis and achieve
fertility,60,61,62 but treatment with FSH, alone or in combination with low doses of
testosterone (insufficient to achieve the high local concentrations of testosterone
required to support spermatogenesis) (Figure 26.3).63

FIGURE 26.3

AGING AND MALE REPRODUCTIVE
FUNCTION

Although aging has adverse effects on male reproductive function, the impact of age is
less obvious than it is in women. Semen quality and male fertility, as well as androgen
production and serum testosterone levels, decrease very gradually as age increases.

Aging and Male Fertility

The relationship between age and fertility in men is more difficult to define than in
women, largely due to the fundamental difference in gametogenesis between the two
sexes. In women, the number of oocytes present at birth inexorably declines as age
advances until it is functionally exhausted at menopause, and fertility declines with the
number of oocytes remaining (Chapter 25). In men, mitotic divisions in the
spermatogonia throughout life replenish the supply of germ cells, and spermatogenesis
continues well into advanced ages, allowing men to reproduce even during senescence.
Although fertility in men does appear to decline as age increases, the effects of age are
much less distinct. The issue may be growing in importance because an increasing
number of men are choosing to father children at older ages. In the United States, birth
rates for men between the ages of 35 and 54 increased by nearly 30% between 1980
(68.2 per 1,000 men) and 2000 (88.3 per 1,000 men).64,65

Semen volume, sperm motility, and the proportion of morphologically normal
sperm, but not sperm concentration, appear to decrease gradually as age
increases.66,67 However, semen characteristics generally do not accurately predict
fertilizing capacity68,69,70,71; neither do endocrine parameters.72,73 A study in a
convenience cohort of nearly 100 men aged 22–80 with no known fertility factors
observed decreases in semen volume (−0.03 mL/year), total motility (−0.7% per year),
progressive motility (−3.1% per year), and total (progressively) motile sperm count
(−4.7% per year).67 Another study that examined the relationship between age and
semen quality among over 400 male partners of women pursuing pregnancy via IVF
using donor oocytes found that total motile sperm count decreased by approximately 2.5
million sperms per year.74

On balance, the available evidence indicates that pregnancy rates decrease and
time to conception increases as male age increases.66,75 In studies of the effect of
male partner age on pregnancy rates, female partner age and declining coital frequency
with increasing age are obvious and important confounding factors.76 A study of the risk
of infertility associated with paternal age, involving over 6,000 randomly selected
European women aged 25–44, observed that the risk of infertility was increased two- to
threefold among women aged 35–39 when the male partner was 40 years or older.77
Others have observed that pregnancy rates for men over 50 are 23–38% lower than for
men under age 3066 and that the probability of achieving pregnancy within a year is
approximately 50% lower for men over age 35 than for those under age 25.78 Results of
a British study (adjusted for partner age and coital frequency) indicate that time to
conception is fivefold longer for men over age 45 than for men under age 25, even when
analysis is restricted to men with young partners.75 Two other studies have suggested

that male fertility may start to decline before age 40.79,80

A study examining the effect of paternal age on pregnancy and live birth rates in
couples undergoing ART found that pregnancy rates declined with each additional year
of age of the male partner.81 Another study of IVF outcomes involving almost 2,000
women with tubal factor infertility (absent or obstructed fallopian tubes) determined
that advanced paternal age (40 years and greater) increased the risk for treatment failure
approximately twofold for women aged 35–40 years and more than fivefold for women
aged 41 and older.82 Within the context of assisted reproduction, the effect of paternal
age is perhaps best assessed in couples using oocyte donation, which makes male age
the dependent variable (because almost all oocyte donors are aged 18–35). However,
data from such studies are conflicting, with some indicating that male age has limited or
no impact on pregnancy, implantation, and live birth rates74,83,84 and others finding that
paternal age is inversely related to reproductive outcomes,85,86 including a decrease in
live birth rates and an increase in miscarriage rates.

There are several possible biologic mechanisms that might contribute to an age-
related decline in male fertility. One involves cellular or physiologic changes in the
male reproductive tract. The testes and prostate exhibit morphologic changes with aging
that might adversely affect both sperm production and the biochemical properties of
semen.87 Autopsy studies of men who died from accidental causes have observed
narrowing and sclerosis of the seminiferous tubules, decreased spermatogenic activity,
and reduced numbers of germ cells and Leydig cells as age increases.88,89 Another
possible mechanism is age-related changes in the hypothalamic-pituitary-testicular axis.
Average FSH levels in men increase after age 30,90 suggesting that the endocrine
environment may begin to change during midlife.91 Decreased semen volume may relate
to reduced androgen-stimulated fluid production in the prostate and seminal vesicles
because testosterone levels decrease with advancing age.92 Whatever the mechanism(s),
decreasing fertility with increasing male age in healthy couples suggests that normal
sperm overproduction may not fully buffer the effects of increasing age. However,
because there is little or no overall measurable decline in male fertility before age
45–50, the available data suggest that male factors likely contribute relatively little
to the overall age-related decline in fertility in women.

Paternal Age and Pregnancy Outcomes

Because male germ cells pass through more mitotic replications than those of females,
there is greater opportunity for error. Older men also are more likely than younger men
to have smoked (and for longer periods of time) and to have been exposed to
gonadotoxins that may cause DNA damage.66,67 Increased paternal age has been

associated with an increase in numerical and structural chromosomal
abnormalities,93,94,95,96,97 with increased DNA fragmentation,98 and with a higher
frequency of point mutations.99 There also is evidence to suggest that increasing male
age may raise the risk of spontaneous abortion in young women.85,86,100

A number of studies have observed that advanced paternal age is associated with an
increase in the prevalence of birth defects (e.g., neural tube defects, cardiac defects,
and limb defects) and congenital diseases (e.g., Wilms tumor).101,102,103,104,105 In a large
population-based retrospective cohort study that included over 5 million births, the
observed overall prevalence of birth defects was 1.5%; compared with infants born to
fathers aged 25–29 years, the adjusted odds ratios for birth defects were 1.04 for infants
with fathers aged 30–35 years, 1.08 for those with fathers aged 40–45 years and 45–50
years, and 1.15 for those with fathers over 50 years old.106 These data suggest that the
risk for birth defects increases only slightly, if at all, with increasing paternal age.

Advanced paternal age has been associated with an increase in new autosomal
dominant mutations (e.g., achondroplasia and Alpert, Waardenburg, Crouzon, Pfeiffer,
and Marfan syndromes).107 At least in theory, this observation might reflect a decrease
in the activity of antioxidant enzymes in the semen and sperms of older men, increasing
their susceptibility to mutation.108 DNA repair mechanisms also may be impaired in
older men. Although the relative risk of autosomal dominant disorders is increased
markedly, the absolute risk is still very small (<1%) because autosomal dominant
diseases are rare.109

Evidence indicates that advanced paternal age is associated with an increased risk
for schizophrenia in offspring110,111,112; overall, the incidence is increased two- to
threefold for children whose fathers are over age 45 years, possibly as a consequence
of mutations emerging during spermatogenesis.113 Similarly, increasing paternal age has
been associated with an increased risk for autism in children, which may reflect de
novo mutations or errors in genetic imprinting.114,115,116,117,118

In older fathers, mutations resulting in X-linked disease also may be more common;
examples include hemophilia A and Duchenne muscular dystrophy.119 The “grandfather
effect” describes their transmission from carrier daughters to affected grandsons.
Overall, advanced paternal age does not appear to be associated with any
significant increase in the risk of fetal autosomal or sex chromosome
aneuploidy.119,120,121,122,123,124 However, available data are limited and confounded by
female partner age. Moreover, results from one study examining the chromosomal
complement of paternal gametes suggest that the incidence of sex chromosome
aneuploidy may increase with age.124 A population-based study involving more than 4

million children observed that paternal age was associated with a small but significant
increase in risk of leukemia and central nervous system cancers.125

It still is not clear whether the risk for miscarriage increases with paternal age,
because results of studies conducted thus far are conflicting, with some finding evidence
for an association with both early and late fetal loss100,126,127 and others not.128,129
Whereas one retrospective study of 558 pregnancies conceived using donor oocytes
observed no association between paternal age and live birth rate,74 another found that
risk for miscarriage increased with paternal age.83 On balance, the weight of
available evidence suggests that advanced paternal age may be associated with a
small increase in the risk of spontaneous abortion. Limited data suggest that advanced
paternal age does not significantly increase the risk for fetal growth restriction130,131 or
stillbirth.132

Androgen Deficiency in the Aging Male

Serum total and free testosterone levels decrease in men as age increases.133
However, unlike the profound estrogen deficiency and associated symptoms that occur
after menopause in women, the age-related decline in androgen levels in men is more
gradual and smaller,134 and the clinical consequences of decreasing androgen levels are
not yet clear.

Serum testosterone concentrations exhibit a distinct diurnal variation in young men
(with highest levels in the morning) but vary relatively little in elderly men.135 In the
cross-sectional European Male Ageing Study, involving 3,220 men aged 40–79 years,
serum total testosterone concentrations fell by an average of 0.4% per year and free
testosterone levels by 1.3% per year.136 Longitudinal studies have observed a somewhat
greater age-related decline in testosterone concentrations and found that levels decrease
at a fairly constant rate.133,137,138 Because sex hormone–binding globulin (SHBG)
concentrations increase gradually with age, free testosterone levels decrease more than
do total testosterone concentrations.134 In the Massachusetts Male Aging Study, free
testosterone levels fell by an average of almost 3% per year.139 SHBG levels also may
rise in association with increased abdominal obesity, further contributing to the
decrease in free testosterone.140

As testosterone levels fall steadily, an increasing percentage of aging men become
hypogonadal, as defined by testosterone concentrations (total testosterone <300–325
ng/dL, free testosterone <5 ng/dL) and/or by signs and symptoms of hypogonadism. In
one population-based observational survey, the prevalence of hypogonadism ranged
from 3% to 7% among men aged 30–69 years and was 18% in men over age 70.141 In a
longitudinal study, serum total testosterone levels in the hypogonadal range were
observed in 20% of men in their 60s, in 30% of those in their 70s, and in 50% of men in
their 80s.133

In some men over age 50, decreasing serum androgen concentrations may be
associated with clinical symptoms and signs of androgen deficiency suggesting
“andropause.” Symptoms of androgen deficiency may include decreased libido,142,143
with or without erectile dysfunction144; reduced strength, energy, or stamina145;
irritability and perceptions of a lower quality of life146; sleep disturbance, depressed
mood, and lethargy141; and changes in cognitive function.147,148 Symptoms may be
accompanied by physical changes, including osteopenia or osteoporosis,149 decreased
muscle mass,150 increased visceral adipose tissue,151 testicular atrophy, and
gynecomastia. Epidemiologic studies have observed that low serum testosterone
concentrations are associated with the development of central obesity, increased insulin

levels, the metabolic syndrome, diabetes, and increased mortality.152,153,154,155 Validated
questionnaires now are available for use in evaluating older men.156,157 However,
scores do not predict or correlate well with measured free and total testosterone
levels158 and therefore lack specificity for the diagnosis of androgen deficiency in the
aging male (ADAM).159,160,161

Men with symptoms or signs of androgen deficiency merit evaluation by
measuring the serum total testosterone level, ideally during the morning hours to
minimize the influence of pulsatile and circadian rhythms in testosterone secretion.
Frankly low concentrations (<200 ng/dL) should be confirmed by repeated
measurements.162 Serum total testosterone includes not only free testosterone but also
testosterone bound to albumin and SHBG. “Bioavailable testosterone” is the sum of free
and albumin-bound testosterone and the measurement that has correlated best with bone
mineral density145 and sexual163 and cognitive function148 in epidemiologic studies.
Because the serum total testosterone level occasionally may be misleading, some prefer
to measure free or bioavailable testosterone, but the accuracy of free testosterone assays
has been challenged164 and neither assay is widely available. A free testosterone index
(FTI) calculated from measurements of total testosterone and SHBG (total
testosterone/SHBG) provides an indirect measure of the amount of bioavailable
testosterone. It is important to emphasize that in men with documented androgen
deficiency, a normal or low serum LH suggests a secondary hypogonadism that
merits additional evaluation by measurement of serum prolactin and magnetic
resonance imaging (MRI) to detect any hypothalamic or pituitary mass lesion.

Treatment

A consensus of expert opinion published in 2002 suggested that a total testosterone
level under 200 ng/dL (6.9 nmol/L) is evidence of hypogonadism that warrants
treatment in symptomatic men, that those with concentrations between 200 and
400 ng/dL (6.9–13.9 nmol/L) may benefit from treatment, and that higher levels all
but exclude androgen deficiency.165 A bioavailable testosterone level below the
normal range for normal young adult men or an FTI less than 0.153 (nmol/nmol) also is
consistent with the diagnosis of androgen deficiency.133 Evidence-based guidelines
issued by the Endocrine Society in 2006 recommended that, in the absence of
pituitary or testicular disease, testosterone therapy be reserved for men with
clearly and consistently low serum total testosterone concentrations (<200 ng/dL)
and clinically important symptoms of androgen deficiency.162

The potential risks of testosterone treatment include fluid retention, gynecomastia,
increased red blood cell mass, worsening of sleep apnea, promotion of benign or

subclinical malignant prostate disease, and possible added risk for cardiovascular
disease.166 Accordingly, the Endocrine Society guidelines recommend against
testosterone treatment in men with prostate or breast cancer, a palpable prostate
nodule or induration, prostate-specific antigen (PSA) greater than 3 ng/mL without
further urologic evaluation, erythrocytosis (hematocrit >50%), untreated
obstructive sleep apnea, severe lower urinary tract symptoms (International
Prostate Symptom Score >19), or class III or IV heart failure.162

Any of the commercial formulations of testosterone may be used for treatment.
Androgen therapy may involve parenteral testosterone esters (75 mg/week or 150 mg
every 2 weeks), implanted pellets (225 mg every 4–6 months), scrotal (40 cm2, one
patch daily) or peripheral skin patches (5 mg, one patch daily), or testosterone gel (5
g/day); treatment should be individualized. At present, there are no data to indicate that
any one formulation is clearly superior. The therapeutic goal is to raise serum
testosterone concentrations over pretreatment values without exceeding the
normal range for young adult men. The target serum testosterone concentration
should be lower than that for younger men (e.g., 300–400 ng/dL) to decrease the
potential risk of testosterone-dependent disease.162 Dehydroepiandrosterone may be
converted to testosterone and is commercially available as an oral dietary health
supplement; standard doses (50–100 mg daily) generally do not raise serum testosterone
concentrations, although higher doses may.167

In randomized, placebo-controlled studies, the effects of testosterone therapy on
bone density have been inconsistent. In one, no overall increase in hip or spine bone
density was observed, but treatment had the greatest effect in men with the lowest
pretreatment testosterone levels.168 In another, testosterone treatment did not increase
bone density but prevented the decrease observed in men receiving placebo.169 In a
third, testosterone treatment (with and without finasteride, which blocks conversion of
testosterone to dihydrotestosterone) increased spine bone density by 9–10% and hip
bone density by 2–3%.170 All three studies168,169,171 and a subsequent systematic
review162 found that testosterone treatment increased fat free mass and decreased fat
mass. However, the increase in lean mass did not result in any consistent improvement
in muscle strength or physical performance.168,169,171 Testosterone treatment also was
not accompanied by any demonstrable improvement in quality of life measures or sexual
function, as judged by questionnaires.168,169

Androgen therapy must be monitored because the long-term health risks and
benefits of treatment have not been established. A baseline physical examination
(breasts, heart, lungs, prostate), serum PSA, and complete blood count should be
obtained; prostate biopsy is recommended when the digital rectal examination or serum

PSA is abnormal. Within 3 months after therapy begins, men receiving androgen therapy
should be evaluated for weight gain and any signs of emerging peripheral edema,
gynecomastia or breast tenderness, sleep disorders, or prostate enlargement.
Recommended monitoring also includes hemoglobin or hematocrit and a serum PSA. A
rapid rise in PSA (>1 ng/mL) soon after treatment begins suggests the possibility of an
undetected prostate cancer and is reason to discontinue treatment pending a thorough
prostate evaluation.172 Serum testosterone also should be measured to ensure that
treatment is achieving the target concentration, but the subjective clinical response is the
most important gauge of the effectiveness of androgen therapy. Men with a good clinical
response, no apparent adverse effects, and normal testosterone levels may continue
treatment but should return for similar monitoring after another 6 months and at least
annually thereafter. If osteoporosis was one of the indications for treatment, bone
mineral density also should be reevaluated approximately 1–2 years after treatment
starts.

In clinical trials of testosterone treatment in elderly men, only a few cases of
prostate cancer have been observed, but statistical power was insufficient to support a
conclusion that testosterone treatment does not increase risk for prostate cancer. A meta-
analysis including 19 trials found that testosterone treatment was associated with a
higher prevalence of elevated PSA values and prostate cancer, although biopsy was
more commonly performed in men receiving treatment.173 There is little evidence that
short-term treatment has adverse effects on the prostate,174 but the effects of long-term
treatment remain uncertain. Similarly, it is not clear whether physiologic testosterone
therapy increases the risk of sleep apnea, because data are conflicting.173,175,176,177
However, testosterone treatment in elderly men clearly can cause erythrocytosis. In
individual studies, up to one-third of treated men have developed an abnormally
elevated hematocrit,170,178 and a meta-analysis concluded that testosterone treatment is
associated with more than a fourfold increased risk for erythrocytosis.173 Taken
together, evidence indicates that testosterone treatment in hypogonadal men has little
effect on serum concentrations of total and low-density lipoprotein cholesterol.179

CAUSES OF MALE INFERTILITY

Male infertility may result from a variety of causes. Some, like ductal obstruction and
hypogonadotropic hypogonadism, can be defined accurately and treated effectively.
Others, like primary testicular failure, can be defined but are not amenable to treatment,
and still others, like seminiferous tubule dysfunction, cannot be corrected but can be
overcome by IUI or ART. Although rare, male infertility also may be the first indication
of a serious underlying medical condition. Unfortunately, much of male infertility is
idiopathic, reflecting our still very poor understanding of the mechanisms that
govern testicular function.

The list of known causes of male infertility is long and varied but can be divided
into four major categories: (1) hypothalamic-pituitary disorders (1–2%), which may be
congenital, be acquired, or result from systemic illness; (2) primary gonadal disorders
(30–40%), both congenital and acquired; (3) disorders of sperm transport (10–20%);
and (4) idiopathic (40–50%). (See Table 26.1 for additional details.)

TABLE 26.1 Causes of Male Infertility



Hypothalamic-Pituitary Disorders

Any hypothalamic or pituitary disease or disorder causing a deficiency of GnRH or
gonadotropins can cause male infertility. The most common congenital cause is
idiopathic isolated gonadotropin deficiency due to absent or defective GnRH secretion
(resulting in sexual infantilism).180 When accompanied by one or more extragonadal
abnormalities, such as anosmia, red-green color blindness, midline facial defects (e.g.,
cleft palate), neurosensory hearing loss, synkinesis (mirror movements), or renal
anomalies, the disorder is known as Kallmann syndrome.181,182,183 A variety of
mutations have been identified in affected men, involving genes encoding cell surface
adhesion molecules or receptors, which are required for normal migration of GnRH
neurons from the olfactory placode to the hypothalamus; examples include KAL1,184,185
fibroblast growth factor 1 (also known as KAL2),186 and prokineticin-2 (PROK2) and
its receptor (PROKR-2).187 Other genetic causes of hypogonadotropic hypogonadism
include rare mutations affecting the GnRH receptor,188 the β-subunit of FSH,43 or
LH37,189,190 or transcription factors involved in pituitary development during
embryogenesis, such as LHX3,191 LHX4, HESX1,192 and PROP-1.193

Hypogonadotropic hypogonadism also can result from hypothalamic disease or
treatments that inhibit GnRH secretion, abnormalities of the pituitary stalk that interfere
with GnRH delivery, and pituitary disease that prevents normal gonadotropin secretion.
Hypothalamic or pituitary tumors can distort the pituitary stalk or compress and
suppress pituitary gonadotropes.

Infiltrative diseases of the hypothalamus or pituitary (sarcoidosis, histiocytosis,
transfusion siderosis, hemochromatosis) can inhibit GnRH or pituitary gonadotropin
secretion.194,195 Hyperprolactinemia from any cause196 and treatment with GnRH
analogs (e.g., for prostate cancer), androgens (e.g., anabolic steroids),197
glucocorticoids,198 or opiates199,200,201 can suppress gonadotropin secretion. Critical
illness202 or injury (e.g., head trauma)203 and chronic systemic illness (e.g., diabetes
mellitus) or malnutrition also have been associated with hypogonadotropic
hypogonadism. Infections (e.g., meningitis) are another rare but recognized cause of
hypopituitarism.204

Obesity in men is associated with hypogonadotropic hypogonadism, involving
several mechanisms.205 Serum free testosterone concentrations are inversely related to
body weight and body mass index, independent of changes in SHBG levels,206,207,208 and
estrogen concentrations are elevated due to increased aromatase activity in adipose
tissue.209 Obstructive sleep apnea is a separate but related additional factor, resulting

in hypoxia.

Primary Gonadal Disorders

Primary gonadal failure (hypergonadotropic hypogonadism) is a major cause of
azoospermia and oligospermia and can result from a variety of congenital or acquired
disorders, including Klinefelter syndrome, Y chromosome deletions, single gene
mutations, cryptorchidism, varicoceles, and other less common causes.

Klinefelter Syndrome

Klinefelter syndrome is one of the most common causes of primary testicular failure,
affecting approximately 1 in 1,000 males,210,211 and is characterized by sex chromosome
aneuploidy. Although an extra X chromosome (47,XXY) is the most common form,
some men with Klinefelter syndrome have a greater or lesser number of X chromosomes
(e.g., 48,XXXY, 46,XY/47,XXY)212; 46,XX males, resulting from translocation of the
testis-determining gene (SRY) to an X chromosome, also have Klinefelter syndrome.
The phenotype varies with the number of extra X chromosomes and possibly also with
the number of trinucleotide CAG repeats on the androgen receptor gene (a
polymorphism); as the length of the repeat sequence increases, receptor activity
decreases. A longer CAG repeat sequence has been associated with taller stature, lower
bone mineral density, gynecomastia, and decreased penile length.213,214

Men with Klinefelter syndrome generally have small, firm testes, resulting
from damage to both seminiferous tubules and Leydig cells. Serum concentrations
of FSH and LH are elevated and testosterone levels are decreased to a varying
extent. Affected men have severely reduced sperm counts and are
undervirilized.212,215 Cryptorchidism is more common in men with Klinefelter
syndrome and causes more severe testicular damage.216

The length of the arms and legs is increased in men with Klinefelter syndrome, due
both to testosterone deficiency and to an independent abnormality of the long bones.
Men with Klinefelter syndrome also exhibit a number of psychosocial abnormalities,217
which have been described as a marked lack of insight, poor judgment, and an impaired
ability to learn from adverse experience.218 They also may have difficulty with complex
speech and a decreased attention span.219 Later in life, they have an increased risk for
developing pulmonary diseases, breast cancer,220 mediastinal germ cell tumors,221
varicose veins and leg ulcers,222 systemic lupus erythematosus,223 and diabetes
mellitus.224

Other chromosomal abnormalities associated with primary gonadal failure include
the 46,XY/45,X karyotype, causing a syndrome characterized by short stature and other

features of Turner syndrome.225 Because the testes may be streak, dysgenetic, or normal,
the phenotype varies from female to normal male. In those with a streak and a
dysgenetic testis (mixed gonadal dysgenesis), the risk of gonadoblastoma is increased
(approximately 20%), and gonadectomy is therefore indicated.

Y Chromosome Deletions

Microdeletions of the long arm of the Y chromosome are now recognized as a
relatively common cause of severe oligospermia and azoospermia, affecting 2–5%
of men with severe oligospermia and 8% of men with azoospermia.226,227 Most map
to the Yq11 region (named azoospermia factor, or AZF), which contains three regions,
AZFa, AZFb, and AZFc. Deletions of the AZFa or AZFb regions typically result in
azoospermia. Mutations in the AZFc region cause infertility of varying severity, ranging
from oligospermia to azoospermia, and are the largest known recurrent deletions in
humans.228,229 The DDx3Y and USP9Y genes, both located in the AZFa region, have
been implicated as having an important role in spermatogenesis; azoospermia is
consistently observed when both are deleted.230,231 Y chromosome deletions also have
been identified in men with cryptorchidism, varicocele, and obstructions of the vas
deferens.232,233

Because all Y chromosome abnormalities will be transmitted to sons of affected
men conceived via ICSI, genetic testing and counseling should be offered to
affected men before their sperms are used for that purpose. Given the importance
and potential consequences of Y chromosome deletions, there is a need to standardize
the tests for their detection.234

Single Gene Mutations and Polymorphisms

Normal male sexual differentiation and spermatogenesis require both normal androgen
production and normal androgen receptors (Chapter 9). The androgen receptor plays an
important role in the differentiation of spermatids and their release from the
seminiferous epithelium. Consequently, it is not surprising that defects in androgen
synthesis or androgen sensitivity are associated with infertility.235,236

As discussed above, the number of trinucleotide CAG repeats in exon 1 of the
androgen receptor gene is inversely correlated with its transcriptional activity.213,214 In
one study in normal fertile men, those with short repeat sequences had the highest sperm
concentrations.237 However, studies in men with idiopathic infertility have yielded
inconsistent results, with some finding an association between longer CAG repeat
segments and male infertility238,239,240 and others not.241 A meta-analysis including 33

studies concluded that men with idiopathic infertility had significantly longer CAG
repeat lengths than did fertile men, suggesting that even subtle abnormalities in
androgen action may adversely affect male fertility.242

Evidence suggests that disorders of estrogen synthesis or action also may be
associated with infertility in men. Impaired spermatogenesis has been observed in mice
and in men lacking a functional estrogen receptor (alpha)243,244 and in mice with an
inactivating mutation in the aromatase enzyme.245 Polymorphisms involving variations
in the number of TA tandem repeats in the promoter region of the estrogen receptor gene
also have been related to sperm production, with higher numbers of TA repeats being
associated with lower sperm counts.246 Inactivating mutations in the FSH receptor gene
are a rare cause of male infertility.39,247

Several other autosomal and X-linked genes have been identified as important
regulators of spermatogenesis. Men with myotonic dystrophy (an autosomal disorder
associated with impaired motor function, cataracts, premature balding, mild mental
retardation, and hypogonadism) also can exhibit abnormal spermatogenesis.248
Mutations in the SYCP3 gene (involved in regulation of the synapse between
homologous chromosomes during meiosis) have been implicated as a potential cause of
male infertility.246 Others include polymorphisms of DAZL (an autosomal homolog of
the DAZ, deleted in azoospermia, gene),249,250,251,252,253 PRM1 and PRM2 (protamines
involved in chromatin compaction), TNP1 and TMP2 (transition nuclear proteins), and
USP26 (deubiquitinating enzyme family).246

Cryptorchidism

Cryptorchidism results from a failure of testicular descent during fetal
development, which is an androgen-dependent process. Consequently, it is common
in men with abnormalities of testosterone production, such as Kallmann syndrome,
androgen resistance, and defects in testosterone synthesis. Cryptorchidism can be
unilateral or bilateral and, in either case, is associated with impaired spermatogenesis
and an increased risk for developing testicular tumors. Even in the absence of
cryptorchidism, the incidence of testicular cancer is increased in infertile men.254,255

In men with cryptorchidism, serum FSH levels often are elevated, but LH
concentrations generally are normal, reflecting normal Leydig cell function. The
severity of the semen abnormality relates to the duration of time the testes have
been outside of the scrotum. Because the testes are more easily retractable early in
life, very young boys may appear transiently to have cryptorchidism, but in most, the
testes descend and remain in the scrotum by age one.256 Men having low serum inhibin

B levels, increased FSH concentrations, and decreased sperm density after repair of
cryptorchidism are at increased risk for infertility.257

Varicoceles

Varicoceles result from dilation of the pampiniform plexus of the spermatic veins in the
scrotum. They are more prevalent in infertile men (up to 30%) than in fertile men (10–
15%) and are 10 times more commonly found on the left than on the right, probably
because the left spermatic vein is longer and joins the left renal vein at a right angle.258
Although increased testicular temperature, delayed removal of local toxins,
hypoxia, and stasis are viewed as the mechanisms likely responsible for the
association between varicoceles and infertility, no causal relationship has been
established.259,260,261

Other Causes of Primary Gonadal Failure

Certain infections are associated with male infertility. Mumps orchitis is widely
recognized as a cause of male infertility. Although rare in prepubertal males, it occurs in
up to 25% of adult men with mumps, some of whom become infertile. The mechanism
may involve damage to the germinal epithelium, ischemia, or immune dysfunction.262,263
Gonorrhea and chlamydial infections also can cause orchitis. Other infections
associated with male infertility include tuberculosis, which may cause epididymal
obstruction, leprosy,264 and human immunodeficiency virus (HIV).265,266

Drugs that can adversely affect spermatogenesis or Leydig cell function include
alkylating agents (e.g., cyclophosphamide, chlorambucil), antiandrogens (e.g.,
flutamide, cyproterone, spironolactone), ketoconazole, cimetidine, and anabolic
steroids.267 Doses of radiation as low as 0.015 Gy (15 rad) can suppress
spermatogenesis, and doses above 6 Gy generally cause permanent azoospermia and
infertility.268

Environmental exposures that may act as gonadotoxins include heat, smoking,
metals, organic solvents, and pesticides. A modest increase in scrotal temperature can
adversely affect spermatogenesis, and a febrile illness can result in dramatic, if also
transient, decreases in sperm density and motility. Hyperthermia also may explain the
infertility associated with spinal cord injuries and chronic sauna or spa exposure.269 In
theory, environmental sources of heat, including tight-fitting underclothing, hot baths and
spas, and occupations that require long hours of sitting (long-distance driving) might
decrease fertility, but none has ever been substantiated in clinical studies.12 Smoking or
heavy use of marijuana, alcohol, or cocaine can decrease semen quality and testosterone

levels.270,271,272

Chronic illness,273 such as chronic renal insufficiency,274 cirrhosis, or
malnutrition,275 can result in primary gonadal failure. Infertility also is common in men
with sickle cell disease, probably due to testicular ischemia.

Disorders of Sperm Transport

Even when sperm production is normal, epididymal obstruction or dysfunction can
result in infertility. The cause of infertility is clear in men with obstruction, but
relatively little is known about epididymal function. Isolated asthenospermia is
presumed to result from epididymal dysfunction, and intrauterine exposure to
diethylstilbestrol may be one cause.276

Congenital or acquired abnormalities of the vas deferens can cause obstruction and
infertility. Approximately 1–2% of infertile men and up to 6% of men with obstructive
azoospermia have congenital bilateral absence of the vas deferens (CBAVD), almost
always related to mutations in the cystic fibrosis transmembrane conductance regulator
(CFTR) gene.277 These men most commonly present with one of two genetic scenarios:
a severe mutation in one allele and a mild mutation, which leaves some residual CFTR
activity, in the other allele; or two mutant alleles with mild effect on the protein. Most
affected men do not exhibit any respiratory and pancreatic disease. Infections
(gonorrhea, Chlamydia, tuberculosis) and vasectomy are other causes of vasal
obstruction. Primary ciliary dyskinesia (Kartagener syndrome) is a genetic disease
that adversely affects cilia structure and function and generally presents as recurrent
sinus and pulmonary infections, bronchiectasis, situs inversus, and male infertility due
to oligoasthenospermia.278,279 Young syndrome is another genetic disease, in which
inspissated secretions in the vas and epididymis result in obstructive azoospermia.280,281

Ejaculatory dysfunction resulting from spinal cord disease or injury,
sympathectomy, or autonomic disease is another cause of infertility relating to disorders
of sperm transport.

THE MALE INFERTILITY EVALUATION

The evaluation of the infertile male should be directed toward achieving all of the
following goals282:

To identify and to correct specific causes of infertility, when possible
To identify individuals whose infertility cannot be corrected but may be overcome
by IUI or use of various forms of ART
To identify individuals having a genetic abnormality that may affect the health of
any offspring that may be conceived through the use of ART
To identify individuals whose infertility can neither be corrected nor overcome
with ART, for whom adoption and the use of donor sperms are options worthy of
consideration
To identify any important underlying medical condition that may require specific
medical attention

Evaluation of the male partner should begin at the same time as in the female
partner, generally when pregnancy fails to occur after 1 year of reasonably regular
unprotected intercourse. Earlier evaluation is indicated for men with any obvious
infertility risk factor, those whose partner is age 35 or older (where it is important to
identify all potential infertility factors as quickly and efficiently as possible), and men
who have reason to question their fertility.

In the male partner, the most relevant parts of the medical history and physical
examination include the following282:

History

Duration of infertility and previous fertility
Coital frequency and any sexual dysfunction
Results of any previous evaluation or treatment for infertility
Childhood illnesses and developmental history
Previous surgery, its indications and outcome, and systemic medical illnesses
Past episodes of or exposures to sexually transmitted infections
Exposures to environmental toxins, including heat
Current medications and allergies
Occupations and use of tobacco, alcohol, and other drugs

Physical Examination

Examination of the penis, to include the location of the urethral meatus

Palpation of the testes and measurement of their size
The presence and consistency of both the vasa and epididymides
Presence of any varicocele
Secondary sex characteristics, including body habitus, hair distribution, and breast
development
Digital rectal examination

A history of cryptorchidism or mumps orchitis suggests the possibility of testicular
atrophy.262,283 The timing and extent of secondary sexual development may alert one to
the possibility of an endocrinopathy. Ductal obstruction can result from sexually
transmitted infections. Diabetes mellitus (bladder neck dysfunction resulting in
retrograde ejaculation) and cystic fibrosis (highly associated with congenital absence of
the vas deferens) are medical illnesses that may hinder fertility in men. Inguinal hernia
repair, renal transplant, and scrotal surgery are associated with risks for unrecognized
injury to the vas deferens.284 Retroperitoneal surgery may disrupt neural pathways and
cause ejaculatory dysfunction; treatment with alpha-blockers, phentolamine,
methyldopa, guanethidine, or reserpine may have similar effects.

When the infertility evaluation is directed by the gynecologist or primary clinician,
physical examination of the male may be deferred pending the results of the first semen
analysis when there is no history of any male genital abnormality, trauma, surgery, or
sexual dysfunction. However, an abnormal reproductive history or semen analysis is
indication for additional formal evaluation that may be conducted by the gynecologist
having the necessary training and experience but is most often performed by the
urologist or other specialist in male reproduction.

Semen Analysis

If a male infertility factor exists, it almost always will be revealed by an abnormal
semen analysis, although other male factors (sexual dysfunction) may be involved even
when semen quality is normal. The initial evaluation for male factor infertility should
include at least one properly performed semen analysis. If abnormal, another
semen analysis should be obtained after at least 4 weeks.282 Semen parameters can
vary widely over time, even among fertile men,285,286,287,288 and also exhibit seasonal
variations.289,290,291 Considering that the overall objective is to gain a sense of the usual
semen quality, over time, more than one analysis is helpful, because a single semen
sample yields only a point estimate that may or may not be representative. However,
with relatively few exceptions, a normal initial semen analysis generally excludes an
important male factor when there is no complaint or suspicion of sexual dysfunction.
Conversely, abnormal semen parameters suggest the need for additional endocrine,
urologic, or genetic evaluation.

Standard but detailed instructions for semen collection should be provided, to
include a defined abstinence period of 2–3 days. Shorter intervals of abstinence
decrease the semen volume and sperm density but generally have little or no impact on
sperm motility or morphology.292 Longer abstinence intervals increase semen volume
and sperm density but also increase the proportion of dead, immotile, or
morphologically abnormal sperm.293 Ideally, the semen specimen should be collected
by masturbation directly into a clean container. If necessary, semen may be collected via
intercourse using a specially manufactured Silastic condom that does not contain
spermicidal agents like those in condoms intended for contraceptive purposes.
Collection after withdrawal during intercourse risks loss of the initial portion of the
specimen, which generally contains the highest concentration of sperms. If possible, the
semen specimen should be collected in a private room within or near the laboratory.
When necessary, the specimen can be collected at home but should be kept at room or
body temperature during transport. Regardless of the method of collection, the semen
sample should be examined within an hour after collection.

Normal Reference Values

The normal reference values in wide use are based on comparisons of the values
observed in the male partners of fertile and infertile couples without specific exclusion
of female infertility factors294,295,296 and therefore do not necessarily represent the
average ranges observed in fertile men. Unfortunately, there is considerable overlap
between the semen parameters observed in fertile and infertile men.297 The normal
reference ranges certainly do not represent the absolute minimum values needed for

conception; many men with values outside the normal ranges are fertile and many with
normal values are nonetheless infertile.297,298,299,300 Values outside of normal ranges
suggest a male infertility factor that may require additional clinical or laboratory
evaluation, but each parameter must be considered in the context of the whole. A
mildly low sperm density may have little significance when semen volume, sperm
motility, and the proportion of abnormal sperms are normal. Conversely, a normal
sperm density offers little reassurance when semen volume is frankly low or the
proportion of motile or normal sperms is grossly abnormal. Overall, the odds of male
infertility increase with the number of major semen parameters (concentration,
motility, morphology) in the subfertile range; the probability is 2 to 3 times higher
when one is abnormal, 5 to 7 times higher when two are abnormal, and 16 times
greater when all three are abnormal.297

Although detailed procedures for semen analysis have been established by the
World Health Organization (WHO), the methods and accuracy of semen analyses as they
are performed in physician offices, hospitals, and specialty andrology laboratories may
vary. Ideally, to ensure accurate and reliable results, semen analyses should be
performed in a laboratory having an established quality control program that conforms
to the standards outlined in the Clinical Laboratory Improvement Amendments (CLIA;
www.hcfa.gov/medicaid/clia/cliahome.htm).301,302 The traditional WHO normal
reference values are shown in Table 26.2.303,304,305

TABLE 26.2 Semen Analysis: Normal Reference Values

Over time, the methods and normal reference values for determining sperm
concentration and motility have changed little, but those for sperm morphology have
changed rather substantially. Using the most recent and rigorous standard, even fertile
men have relatively few normal sperms. The rationale for the change in the morphology
standard and its clinical relevance are discussed below (see Sperm Morphology).

In 2010, the WHO published revised lower reference limits for semen analyses,
which represent the fifth centile in a population of over 1,900 men from 8 countries on 3
continents whose partners conceived within 12 months (Table 26.3).306

TABLE 26.3 Semen Analysis: Lower Reference Limits
(95% CI) in Fertile Men

These data provide clinically relevant reference values for use in the evaluation of
infertile men and in assessing their prognosis for achieving pregnancies with their
partners.

Ejaculate Volume and pH

A low or absent ejaculate volume suggests the possibility of failed emission, incomplete
collection, a short abstinence interval, CBAVD, ejaculatory duct obstruction,
hypogonadism, or retrograde ejaculation. Other semen parameters can help to
differentiate the cause.

The majority of semen volume comes from the seminal vesicles, which share a
common embryology with the vasa deferentia. Seminal vesicle secretions are
alkaline and contain fructose. Because the seminal vesicles are hypoplastic or absent in
most men with CBAVD, they generally produce a low-volume acidic (pH < 7.2)
ejaculate that contains little or no fructose and reflects the greater contribution of acidic
prostatic secretions.307,308,309 Men with ejaculatory duct obstruction produce an
ejaculate having similar characteristics because the ejaculatory ducts are formed by the
union of the vasa with the ducts exiting the seminal vesicles, proximal to the prostate;
semen fructose concentrations decrease with increasing severity of ejaculatory duct
obstruction.310,311,312 When both ejaculatory ducts are completely obstructed, the

semen is acidic (containing only prostatic secretions) and contains neither fructose
nor sperms. Hypogonadal men with either primary or secondary testicular failure also
may exhibit low ejaculate volumes because the secretions of the seminal vesicles and
prostate are stimulated by androgens; volume is therefore decreased when androgen
levels are low.

A postejaculatory urinalysis can detect retrograde ejaculation and should be
considered whenever the ejaculate volume is less than 1 mL, except when
hypogonadism, CBAVD, collection problems, or a short abstinence interval offers
an obvious explanation. When indicated, the postejaculatory urinalysis involves
centrifugation for 10 minutes at no less than 300g, followed by microscopic examination
of the pellet (400×). In men with no or low semen volume and azoospermia (no
sperms in the ejaculate), the observation of any sperm on postejaculatory
urinalysis suggests retrograde ejaculation. More substantial numbers of sperms must
be observed in men with low-volume oligospermia before making the diagnosis of
retrograde ejaculation because sperms found in the urine may simply have been washed
from the urethra during urination.307

Sperm Concentration and Total Sperm Count

Azoospermia describes the absence of sperms on standard microscopic examination.
The prevalence of azoospermia is approximately 1% in all men313 but up to 10–15% in
infertile men.314 To establish the diagnosis, the semen specimen should be centrifuged at
high speed (3,000g for 15 minutes) and the pellet examined at high magnification
(400×)305; the absence of sperms should be documented on at least two separate
occasions. Azoospermia is generally classified as obstructive (normal sperm
production) or nonobstructive (decreased or absent spermatogenesis).

Obstructive azoospermia may result from a blockage anywhere in the ductal system,
from the efferent ductules to the ejaculatory ducts, as the consequence of severe
infection, iatrogenic injury during scrotal or inguinal surgery, or congenital anomalies
(CBAVD); approximately 40% of azoospermic men have an obstruction.307
Nonobstructive azoospermia is caused by intrinsic testicular disease (primary testicular
failure) or endocrinopathies and other conditions that suppress spermatogenesis
(secondary testicular failure). Men with nonobstructive azoospermia may have low-
level sperm production that is insufficient to drive epididymal transport and to permit
sperms to enter the ejaculate.315 Careful examination of a centrifuged semen sample will
identify sperms in the ejaculates of up to one-third of men with a preliminary diagnosis
of nonobstructive azoospermia.316 The observation has practical significance because
men in whom even a modest number of sperms can be recovered from the ejaculate may

not require surgical sperm retrieval for IVF (testicular sperm extraction, TESE).

Oligospermia is defined traditionally by a sperm density less than 20 million/mL
and is considered severe when the sperm concentration is below 5 million/mL. The
probability of conception increases with increasing sperm concentrations up to
approximately 40–50 million/ mL but does not rise further with higher sperm
densities.297,298 The results of a large US study comparing semen parameters in fertile
and infertile men with normal partners indicate that the likelihood of male infertility is
increased approximately fivefold (5.3, 95% CI = 3.3–8.3) when sperm density is less
than 13.5 million/mL.297 In an earlier European study of similar design, the density
representing the tenth percentile for fertile men was 14 million/mL.317 These values are
consistent with the most recent recommendations from WHO regarding the lower
reference limit for fertile men (15 million/mL).306 Oligospermia may be associated with
a varicocele, hypogonadism, or specific microdeletions in the Y chromosome.
Endocrine and genetic evaluation is indicated for men with severe oligospermia
(discussed below).

Total sperm count is simply the product of multiplying the semen volume and sperm
concentration. The total sperm count may be normal in oligospermic men when volume
is high and also normal when volume is low but density is high. The two parameters
fluctuate and must be considered together in making judgments regarding semen quality.
Numerous studies have suggested that the average sperm count in men has been
decreasing steadily over the past few decades,318,319 raising concerns that environmental
toxins and chemicals having estrogen-like activity (xenoestrogens) might be
responsible. However, numerous others have observed no evidence of any significant
change.320,321,322,323,324,325 Most importantly, the prevalence of infertility has not
increased significantly over the same intervals, indicating that any decrease in semen
quality that may have occurred has had no global clinical impact.

Sperm Motility, Forward Progression, Total Motile Count,

and Vitality

Sperm motility is estimated as a percentage of the total sperm population exhibiting any
motion. Forward progression generally is graded on an arbitrary scale (grade 0–4) and
most often reported as the percentages exhibiting rapid (grade 3–4), slow (grade 2), and
nonprogressive motility (grade 0–1). Total progressive motility generally represents an
estimate of the percentage of sperms exhibiting purposeful forward motion (grade 2–4).
The probability of conception rises with increasing motility up to approximately
60%.297 According to one large US study, the likelihood of male infertility is increased
approximately fivefold (OR = 5.6, 95% CI = 3.5–8.3) when progressive motility is less

than 32%.297 In another study, the threshold separating fertile and infertile men was 45%
and the tenth percentile motility for fertile men was 28%.317 Again, these values
compare well with the lower reference value for progressive motility now
recommended by the WHO (32%).306

The total motile sperm count is calculated from the total sperm count and the
percentage of progressively motile sperm and represents an estimate of the total number
of active sperms in the ejaculate. Allowing for the inevitable procedural losses
associated with processing a semen sample for IUI (up to approximately 50%), the total
motile sperm count can be used to estimate the likely processed total motile sperm
count, which correlates with the probability of pregnancy achieved with IUI in the
treatment of male factor infertility (see Treatment, below).326,327,328,329,330

In general, poor sperm motility (asthenospermia) suggests testicular or epididymal
dysfunction. Asthenospermia has been associated with sperm autoantibodies
(predisposing to aggregation), genital tract infections (leukocytes in the semen), partial
obstruction of the ejaculatory ducts or at the site of a vasectomy reversal
(reanastomosis), varicoceles, and prolonged abstinence intervals.

Large numbers of viable nonmotile sperms suggest the rare possibility of primary
ciliary dyskinesia (Kartagener syndrome), in which sperm tails have a structural
abnormality and cannot flagellate. The cilia of the respiratory tract usually also are
involved; affected individuals are infertile and predisposed to chronic respiratory tract
infections. Diagnosis is made by examination of sperms using electron microscopy.

When no motile sperms are observed, a sperm vitality test can differentiate
viable nonmotile sperms from dead sperms. One method involves mixing fresh semen
with a supravital dye (eosin Y or trypan blue); sperms with intact membrane function do
not take up the stain. Another method, the hypo-osmotic sperm swelling test, involves
incubation of sperms in a hypo-osmotic solution; the tails of sperms with normal
membrane function swell and coil as fluid is transported across the membrane. In men
with few or no motile sperms, the hypo-osmotic swelling test can be used to identify
living nonmotile sperms for ICSI.331

Sperm Morphology

Sperm morphology reflects the quality of spermatogenesis. Morphologic abnormalities
(teratospermia) are categorized by location, involving the head, neck (midpiece), or
tail. Cytoplasmic droplets in the midpiece that occupy more than approximately one-half
of the area of a normal sperm head represent another specific defect. Sperms classified
as normal must be normal in all respects. Teratospermia has been associated with
varicocele and with both primary and secondary testicular failure. It may be observed in

association with abnormalities in sperm concentration and motility or occur as an
isolated abnormality.

The most recent WHO reference values (since 1999) for the evaluation of sperm
morphology are very similar to those known as the Kruger (Tygerberg) or “strict”
criteria,332,333 which arose from efforts to identify predictors of fertilization in IVF
cycles. When sperm morphology was judged according to a strict normal standard,
fertilization efficiency in vitro correlated with the percentage of morphologically
normal sperms.332,334,335 Conventional fertilization rates were highest when the
percentage of normal sperms was 14% or higher, very poor (7–8%) when less than 4%
of sperms had normal morphology, and intermediate when values fell between the two
threshold values.332 After several studies confirmed the predictive value of strict sperm
morphology in IVF,336,337,338,339,340,341,342,343 severe teratospermia (0–4% normal sperms
by strict criteria) became widely accepted as an indication for ICSI in IVF cycles.
However, others have observed no differences in the fertilization, pregnancy, and live
birth rates achieved with ICSI and conventional fertilization and argue that isolated
teratospermia is not a valid indication for performing ICSI.344,345,346,347 Controversy
continues, but strict sperm morphology remains the best available predictor of
sperm function (the capacity to fertilize a mature oocyte).

It was logical to anticipate that if strict sperm morphology could predict fertilization
efficiency under optimized conditions in vitro, it also might have value for predicting
the likelihood of successful fertilization in vivo and help to discriminate fertile and
infertile men. A number of studies have examined semen parameters in couples with no
known infertility factors who were attempting pregnancy,298,348 or compared the semen
parameters of fertile and infertile men297,317,341,349; two have included only men whose
partners had no apparent infertility factors.297,317 Whereas sperm concentration and
progressive motility had value for distinguishing fertile from infertile men, strict
sperm morphology (as determined by an individual having extensive training and
experience) was the one most discriminating value.297,317 In the larger of the two
studies, the likelihood of male infertility was increased approximately fourfold (OR =
3.8, 95% CI = 3.0–5.0) when strict sperm morphology was less than 9% normal.297 The
9% threshold value had a sensitivity of 43% and a specificity of 81% for identifying
infertile men; lowering the threshold value to 5% normal forms decreased sensitivity to
only 19% but increased specificity to 94%.297 In a smaller study of similar design, the
threshold value that identified infertile men was 10% and the value corresponding to the
tenth centile among fertile men was 5% normal forms.317

Strict sperm morphology is perhaps most relevant for couples with mild
oligospermia or asthenospermia or with unexplained infertility (normal ovulatory

function, female reproductive anatomy, and semen parameters). In such couples, IUI
(with or without ovarian stimulation) and IVF are the treatment options that offer the
greatest likelihood for success (Chapter 27). Most,350,351,352,353 but not all,354,355 studies
have observed that cycle fecundability in IUI cycles correlates with the proportion of
morphologically normal sperms and is generally poor when strict morphology is less
than 5% normal. Although no threshold value excludes the possibility of pregnancy
with expectant management or IUI, the relationship between strict sperm
morphology and cycle fecundability with IUI merits careful consideration and
discussion when planning treatment for couples with male factor and unexplained
infertility. Other important considerations include age of the female partner, the
duration of infertility, and the comparative costs, logistics, risks, and prognosis
associated with alternative treatment strategies, including IVF with and without ICSI.

It is important to emphasize that strict sperm morphology values, like other semen
parameters, vary among specimens within individuals, among technologists within
laboratories, and among laboratories.333,356 A rigorous quality control program helps to
ensure accuracy and consistency.357,358 Unfortunately, relatively few of the laboratories
that perform routine semen analyses have sufficient test volume and the highly trained
and experienced personnel required to provide a valid assessment of strict sperm
morphology. Consequently, earlier WHO standards for sperm morphology (1987,
1992) that classify more sperms as normal are still widely used in most hospital
laboratories.303,304 Although morphology assessments using the earlier standards have
little value, results for semen volume, sperm concentration, and motility are still
informative and can reveal an obvious male factor. However, a more sophisticated
semen analysis, including strict sperm morphology, merits serious consideration before
implementing treatment for couples with male factor or unexplained infertility.

Round Cells and Leukocytospermia

Epithelial cells, prostate cells, immature sperm (round spermatids, spermatocytes), and
leukocytes all appear as “round cells” and cannot be differentiated in a routine semen
analysis. When the round cell count exceeds 5 million/mL, additional studies should
be performed to differentiate leukocytes from immature sperms and to identify
those men having true leukocytospermia (>1 million leukocytes/mL) who may
require additional evaluation for genital tract infection or inflammation. Any of a
variety of special stains, biochemical tests, and immunohistochemical techniques can be
used to identify the proportion of round cells that is leukocytes.359,360 Although
leukocytospermia has been implicated as a cause of poor sperm motility and function,361
more recent studies have failed to demonstrate any association between the
leukocytospermia in men with chronic prostatitis and abnormal semen parameters.362

Nevertheless, documented leukocytospermia generally is regarded as an indication for
semen culture (Mycoplasma hominis, Ureaplasma urealyticum, Chlamydia). When
cultures are performed, the penis should be washed carefully with Betadine before
sample collection to reduce the likelihood of contamination from skin flora. For reasons
unknown, leukocytospermia unrelated to infection or inflammation also may be
observed in the semen of men with spinal cord injuries.363

Semen Viscosity

The viscosity of semen is evaluated routinely and graded on an arbitrary scale (grade 0–
4). Seminal hyperviscosity is relatively uncommon and its causes have not been clearly
defined. Not surprisingly, hyperviscosity has been associated with
asthenospermia.364,365 Although genital tract infections and sperm autoantibodies have
been implicated as causes of seminal hyperviscosity, evidence for the association is
lacking.366 Like abnormalities of pH and fructose levels, increased semen viscosity
suggests the possibility of dysfunction in the accessory glands (prostate, seminal
vesicles),367 but in practice, the parameter has relatively little importance.

Specialized Tests

Although all of the major semen parameters (concentration, motility, morphology) have
impact on fertility when clearly abnormal, they do not measure or answer what is
arguably the most important question: can the sperm effectively attach to, penetrate, and
fertilize the partner’s ova? Strict sperm morphology is a useful indirect measure of
sperm function by virtue of its correlation with fertilization rates in vitro, but the
parameter leaves much to be desired and generally is available only in specialty
andrology laboratories associated with IVF centers.

Unfortunately, although a wide assortment of specialized tests and procedures
has been developed to evaluate sperm attachment to the zona pellucida,
penetration of the oocyte membrane, or the release of acrosomal enzymes, we still
have no reliable validated test of sperm function. Because we do not yet understand,
cannot measure, and have no way to correct a suspected sperm function abnormality,
attention has focused on ICSI as a way to negate or circumvent sperm function
abnormalities. However, the need for a reliable sperm function test persists, because
IVF and ICSI are not practical options for a great many infertile couples and all would
like to use their available time and resources in the most efficient and effective way
possible368; the time and expense associated with treatments involving IUI might be
avoided if there was good evidence to indicate that only ICSI offered a realistic
likelihood for success.

Sperm Autoantibodies

The blood-testis barrier normally isolates sperms from immune recognition (sperms
develop after immunocompetence is established), but if it is disrupted and sperms are
exposed to blood, an antigenic response may result. Risk factors for antisperm
antibodies include ductal obstruction, previous genital infection, testicular torsion or
trauma, and sterilization reversal (vasovasostomy or vasoepididymostomy).369 Sperm
autoantibodies can be found in the serum, but evidence indicates they have no clinical
significance.370,371 In contrast, antibodies bound to sperm may be clinically relevant
because they may interfere with sperm motility or prevent fertilization.372,373

Marked sperm clumping or agglutination, like isolated asthenospermia, may signal
the presence of sperm autoantibodies, but neither is observed commonly. Some also
regard unexplained infertility as an indication for antisperm antibody testing. The two
most widely used tests for detection of sperm autoantibodies involve the use of beads or
latex particles with attached antibodies (raised against human immunoglobulins) that
bind to antibodies on the surface of sperms.305 The threshold for a positive test is not
well established, but antibodies generally are considered clinically important when

more than 50% of sperms are coated. However, the levels of antibody can fluctuate,
even without treatment.374 New research on sperm proteomics may help to link specific
sperm proteins with their functions and to identify relevant sperm autoantibodies.375

Pregnancy rates are reportedly lower for men with demonstrable antisperm
antibodies than for those without antibodies, and among those with antisperm
antibodies, pregnancy rates are lower when more than 50% of sperms are antibody
bound.376 Antisperm antibodies have been associated with poor postcoital test results,
but routine postcoital testing is no longer performed because results have no proven
value (Chapter 27). Because IUI was among the most popular and effective treatments
for antisperm antibodies377 (as it was for presumed cervical factor infertility) and IUI
has become a core element of most treatments for unexplained infertility other than IVF
(Chapter 27), the results of antisperm antibody testing, like those from postcoital testing,
rarely offer any information that affects treatment decisions or outcomes. Sperm
autoantibody testing is seldom any longer performed because when IUI fails or IVF
is otherwise indicated, ICSI can effectively circumvent any adverse effects of
antisperm antibodies.378

Sperm Penetration Assay

The zona pellucida surrounding the oocyte blocks entry of more than one sperm and
fertilization by sperms of a different species, but if removed by gentle enzymatic
digestion, sperms of another species can penetrate the egg. In the sperm penetration
assay, zona-free eggs collected from superovulated golden hamsters are incubated with
washed human sperms, and the proportion of eggs penetrated or the number of sperm
penetrations per egg by the sperms of the test subject is compared to that observed in a
parallel incubation using sperms from a known fertile individual.305,379,380 In theory, the
test evaluates four specific sperm functions: capacitation, the acrosome reaction, fusion
with the oolemma, and decondensation within the egg cytoplasm.

Unfortunately, the results of the sperm penetration assay are quite sensitive to
varying culture conditions and the test procedure has been difficult to standardize. The
test relies on spontaneous in vitro or chemically induced acrosome reactions.381 Test
results also vary over time and even proven sperm donors may fail the sperm
penetration assay on a given occasion.382 The predictive value of the sperm penetration
assay for IVF or natural conception among infertile couples has varied widely among
studies and depends, in large part, on the experience of the individual
laboratory.383,384,385,386 Interestingly, test results also have not consistently correlated
with strict sperm morphology, the most commonly accepted predictor of
fertilization.387,388,389 Perhaps most importantly, the test is cumbersome, costly, time-

consuming, and not widely available.

Human Zona Binding Assay

Whereas sperm penetration of zona-free eggs may test the ability of sperms to penetrate
the oocyte, it does not, by definition, test the ability of sperms to bind to and penetrate
the zona pellucida. The hemizona assay uses bisected zonae derived from human
oocytes not previously exposed to sperms and compares the binding of test subject and
fertile control sperms.390,391 Results have been used to predict fertilization in
vitro,392,393 but the limited availability of human zonae and the technical aspects of the
test effectively preclude application beyond use as an investigative tool.

Computer-Assisted Sperm Analysis

Computer-assisted sperm analysis (CASA) was developed in efforts to establish a
precise, automated, and objective evaluation of sperm concentration and motion
characteristics (velocity and head movement). The technology employs sophisticated
instruments to generate digitized video images for analysis, but its accuracy is highly
dependent on the methods of sample preparation, frame rate, and sperm
concentration.394,395 Although some have found that sperm motility characteristics have
predictive value for fertilization in vivo and in vitro, others have not.396,397,398

Acrosome Reaction

The acrosome is a membrane-bound structure located at the tip of the sperm head
containing proteolytic enzymes necessary for penetration of the zona pellucida (Chapter
7), and acrosin is one of those enzymes.399 The acrosome reaction involves the fusion of
the acrosome and the plasma membrane, followed by release of the acrosomal enzymes
and exposure of the sperm head, which must occur after sperm binding to the zona
pellucida. The sperms of infertile men exhibit an increased prevalence of spontaneous
acrosome loss and decreased acrosome reactivity in response to treatment with a
calcium ionophore.400 However, the clinical relevance of acrosin measurements and
abnormal acrosome reactivity in vitro remains to be established.

Biochemical Tests

Biochemical tests of sperm function include measurements of sperm creatine
phosphokinase and reactive oxygen species. Creatine phosphokinase is an important
enzyme involved in the generation, transport, and use of energy within the sperm.
Studies of the levels or forms of the enzyme in the sperms of fertile and infertile men

have yielded conflicting results.401,402

Normal oxygen metabolism generates reactive oxygen species, which may be toxic
in excess. In both fertile and infertile men, leukocytes are the principal source of
reactive oxygen species, but sperms themselves also produce them. Increased levels
have been observed in the semen of infertile men and implicated as a cause of otherwise
unexplained male infertility.403,404,405 Peroxidation of sperm lipid membranes and
generation of toxic fatty acid peroxides may interfere with sperm functions.406 Reactive
oxygen species can be detected with chemiluminescent probes, but such tests remain
investigational.

Sperm Chromatin Structure and DNA

A significant proportion of infertile men have increased levels of DNA damage that may
adversely affect fertility407,408,409,410,411,412,413 even when all standard semen parameters
are normal.414 Men with abnormal semen parameters often exhibit high levels of DNA
fragmentation, but the same can be observed in men with normal semen
parameters.407,411,415,416,417 Recently developed tests of sperm chromatin structure and
DNA fragmentation provide a measure of sperm chromatin and nuclear integrity,418 but
their clinical utility has not been established. A meta-analysis including 13 relevant
studies involving over 2,000 treatment cycles concluded that the small association
between sperm DNA integrity test results and pregnancy in IVF and ICSI cycles is not
sufficient to warrant their routine use in the evaluation of infertile men.419

Endocrine Evaluation

Endocrine disorders involving the hypothalamic-pituitary-testicular axis are well
recognized but uncommon causes of male infertility and are extremely uncommon in men
having normal semen parameters. Indications for endocrine evaluation in infertile
men include an abnormal semen analysis (particularly a sperm concentration <10
million/mL), sexual dysfunction (decreased libido, impotence), and other clinical
symptoms or findings that suggest a specific endocrinopathy.307 A basic endocrine
evaluation of the infertile male involves measurements of serum FSH and total
testosterone and will detect the vast majority of clinically significant
endocrinopathies.420

When the total testosterone level is low (<300 ng/dL), the assay should be repeated
to confirm the finding, and a serum free testosterone, LH, and prolactin should be
obtained.307,421 Together, the levels of FSH, LH, and testosterone help to differentiate
the clinical condition. In men with hypogonadotropic hypogonadism, generally all
three hormone levels are distinctly low. In men with abnormal spermatogenesis, the
FSH level may be normal or high and LH and testosterone levels are normal. Those
with testicular failure exhibit high levels of FSH and LH and a low or normal
testosterone concentration. Men with a prolactin-secreting pituitary tumor
generally have normal or low gonadotropin concentrations, a low serum
testosterone, and an elevated prolactin level. In those with hypogonadotropic
hypogonadism, with or without hyperprolactinemia, MRI of the hypothalamic-
pituitary region is indicated to exclude a mass lesion.

In infertile men with severe oligospermia (<5 million/mL), low testosterone levels
(<300 ng/dL), and normal gonadotropin concentrations, evaluation might be expanded to
include a serum estradiol and calculation of the testosterone (ng/dL)/estradiol (pg/mL)
ratio, because those with low values (<10) may benefit from treatment with an
aromatase inhibitor.422,423

Urologic Evaluation

If not performed earlier, grossly abnormal semen parameters are indication for a
thorough physical examination by a urologist or other specialist in male
reproduction; some men also may require further urologic evaluation.

In normal men, the testes are firm and measure 15–25 mL in volume.424 Small soft
testes suggest testicular failure. Epididymal fullness suggests obstruction in men with
azoospermia.425 The diagnosis of CBAVD is made by physical examination alone and
does not require scrotal sonography or exploration.308,309 Palpation of the spermatic
cord (erect and supine, with and without Valsalva) may reveal a varicocele,426 which
can be graded (grade 1–3) according to severity.427 Digital rectal examination defines
the size and symmetry of the prostate and may reveal the presence of midline cysts or
dilated seminal vesicles suggesting ejaculatory duct obstruction.

Transrectal ultrasonography is indicated for the diagnosis of ejaculatory duct
obstruction in men with severe oligospermia or azoospermia, palpable vasa, low-
volume ejaculates, and normal testis volume, particularly when the semen is acidic and
contains little or no fructose.307,428 Vasography offers an alternative method for
diagnosis of ejaculatory duct obstruction, but transrectal ultrasonography is less
invasive and avoids the risk of vasal injury.429 Observations of midline cysts, dilated
seminal vesicles, or ejaculatory ducts suggest, but do not establish, the diagnosis of
ejaculatory duct obstruction. Conversely, the absence of any such findings does not
exclude the possibility. Seminal vesicle aspiration and vesiculography under transrectal
ultrasound guidance provides the means to make a definitive diagnosis; any sperms
retrieved can be cryopreserved for use in IVF with ICSI.430 Definitive treatment
requires transurethral resection of the ejaculatory ducts.431

Transscrotal ultrasonography can help to clarify uncertain physical findings or to
confirm the presence of a scrotal mass. It also may reveal nonpalpable varicoceles, but
there is no evidence to indicate they have clinical importance.282

Renal ultrasonography is indicated for men with unilateral or bilateral vasal
agenesis. Approximately 25% of men with unilateral vasal agenesis and 10% of men
with CBAVD have unilateral renal agenesis.432

Testis biopsy may be performed for diagnostic purposes in azoospermic men.
Those with elevated serum FSH levels do not require a diagnostic biopsy because a
high FSH concentration is diagnostic for abnormal spermatogenesis. Although biopsy
may be performed to determine the likelihood that sperms can be retrieved for IVF with
ICSI, results may not be all that helpful because sperm production can be limited to

specific foci within the testes. In contrast, diagnostic biopsy is indicated for
azoospermic men with normal testicular size, at least one palpable vas deferens and a
normal serum FSH level, because the normal FSH does not guarantee that
spermatogenesis is normal. When biopsy is performed, a portion of testicular tissue can
be cryopreserved for use in a future IVF/ICSI treatment cycle to avoid the need for a
second procedure. A biopsy that reveals normal spermatogenesis implies obstruction at
some level, which then must be defined by surgical exploration with or without
vasography (see Surgical Treatment, below).307

Genetic Evaluation

Genetic abnormalities may cause infertility by interfering with sperm production or
transport. Currently, those most relevant to male infertility and its treatment include (1)
mutations within the CFTR gene, which are highly associated with CBAVD, (2)
chromosomal anomalies resulting in testicular dysfunction (Klinefelter syndrome;
47,XXY), and (3) Y chromosome microdeletions associated with abnormalities of
spermatogenesis. These conditions have implications that extend beyond their
association with azoospermia and severe oligospermia because they can have
consequences for the offspring of affected couples. Ideally, genetic counseling should be
offered both before and after genetic testing.

Mutations of the CFTR gene are highly associated with CBAVD; almost all
men with cystic fibrosis have CBAVD and at least two-thirds of men with CBAVD
have a demonstrable CFTR mutation.433,434 The gene encodes a protein involved in
the formation of the seminal vesicles and the reproductive ductal system in men.
Although approximately 4% of Caucasian men carry a known CFTR gene mutation,
clinical CBAVD is much less common because penetrance is low in heterozygous
individuals.435 Common speculation, and the prudent clinical assumption, is that
virtually all men with CBAVD may have such mutations, some of which have a low
carrier frequency and have simply not yet been defined. It is important to note that the
spectrum of vasal aplasia includes not only CBAVD but also unilateral absence of the
vas deferens, bilateral partial absence of the vas or epididymides, and epididymal
obstruction. Men with CBAVD or less severe forms of vasal aplasia, and their
female partners, should be screened for CFTR mutations before any attempts at
pregnancy via ART to determine the risk for transmitting cystic fibrosis or CBAVD
to offspring.

The overall prevalence of chromosomal anomalies in infertile men is
approximately 7% and inversely related to sperm concentration; the prevalence is
highest in azoospermic men (10–15%), lower in oligospermic men (approximately 5%),
and very low in men with normal semen quality (<1%).436,437 By far, the most common
chromosomal anomaly in infertile men is Klinefelter syndrome (47,XXY,
46,XY/47,XXY), which accounts for about two-thirds of chromosomal abnormalities in
infertile men.438 Structural chromosomal abnormalities (translocations, inversions)
make up the majority of the remainder.439 The partners of affected men are at increased
risk for miscarriage and birth of children with aneuploidy and congenital anomalies.
Karyotyping should be offered to men with nonobstructive azoospermia or severe
oligospermia (<5 million/mL) before their sperms are used for IVF with ICSI.307
Embryo biopsy and preimplantation genetic diagnosis using fluorescence in situ

hybridization or other techniques to evaluate chromosomal composition can be used to
identify normal embryos suitable for transfer.440

Approximately 8% of azoospermic and 2–5% severely oligospermic infertile men
harbor a Y chromosome microdeletion that cannot be detected with a standard
karyotype but can be identified using more sophisticated genetic techniques.226,227,441
Most such microdeletions occur in regions of the long arm of the Y chromosome (Yq11),
designated as AZF (azoospermic factor) a (proximal), b (central), and c (distal), which
appear to include genes necessary for normal spermatogenesis.442 Many men with
microdeletions in the AZFc region are only severely oligospermic,443,444 and those who
are azoospermic generally produce sufficient sperms to allow their recovery by testis
biopsy. In contrast, the prognosis for sperm recovery in men with microdeletions in the
AZFa or AZFb region is very poor.445,446,447 Microdeletions in the AZFd region are
associated with normal spermatogenesis, and their clinical significance is unknown.448

Sons of men with Y chromosome microdeletions can be expected to inherit the
defect and its clinical consequences.449,450,451 Until recently, infertility was the only
known clinical consequence of Y microdeletions, but a 1.6-Mb deletion that removes
part of the AZFc region (known as the gr/gr deletion) now has been associated with an
increased risk for developing testicular germ cell tumors.452 Screening for Y
chromosome microdeletions should be offered to all men with nonobstructive
azoospermia or severe oligospermia (<5 million/mL) who are candidates for IVF
with ICSI.307

MEDICAL TREATMENT FOR MALE
INFERTILITY

With a few specific and important exceptions, male infertility generally is not amenable
to medical treatment. Careful evaluation can identify those men with treatable
conditions who may benefit from medical therapy.