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Absence of Sperm
Azoospermia: Absence of Sperm
Azoospermia is the absence of spermatozoa in the
semen or the failure of formation of spermatozoa. It can arise as a
result of primary testicular failure, obstruction or previous
vasectomy. Complete azoospermia signifies infertility.
Common causes of azoospermia include:
Primary testicular failure
This may be due to genetic defects, undescended
testes, physical injury to the testes or mumps occurring after
puberty. Often the cause is unknown. Patients with primary
testicular failure usually have small, soft testes and a grossly
elevated plasma FSH. Although undescended testes may be surgically
corrected, the chance of restoring fertility is
remote.
Obstruction
This is the second major cause of azoospermia. It
is sometimes amenable to surgery and surgical exploration can be
undertaken in patients with normal size testes and with a normal
FSH. The results of surgery depend on the location of the blockage
and there is at best a 50% success rate in those patients with an
obstruction in the cauda epididymis due to gonorrhoea.
Sexually transmitted diseases may cause
epididymitis and lead to blockage of the ductal system, resulting
in permanent azoospermia. Obstructive azoospermia can also be due
to agenesis (absence) of the epididymis and other parts of the
ductal system, including the vas deferens. Some of these cases seem
to be of genetic origin. Congenital bilateral agenesis of the vas
deferens is found in most patients with cystic fibrosis. It has
been shown that point mutations of the cystic fibrosis gene may be
present in at least two-thirds of men with isolated bilateral
agenesis of the vas deferens without any other symptoms of cystic
fibrosis. This means that men with agenesis of the vas deferens who
produce sperm, and are thus suitable for ART, must be counselled
about the risk of cystic fibrosis in any child
produced.
Previous vasectomy
This is an increasingly common cause of
azoospermia in Western countries and in countries such as India
where it is a favoured method of contraception.
Absence of germ cells
In many men with azoospermia, the seminiferous
tubules contain only Sertoli cells. This can result from numerous
causes, including cytotoxic drugs, irradiation or due to factors
present during foetal life. However, in most cases the aetiology is
unknown.
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