In the human,
the process of spermatogenesis starts at puberty and continues throughout life.
The total process of spermatogenesis in humans takes 74 days within the
seminiferous tubules. It takes a further ten days for the sperm to travel to
the epididymis to be stored for use during ejaculation. The head of the epididymis
stores 70 per cent of the mature sperm and, during ejaculation, the sperm exit
via the vas deferens which then passes through the inguinal canal and opens
into the urethra adjacent to the prostate.
The supporting
cells of the testis are the Leydig and Sertoli cells. The Leydig cells are
contained in the connective tissue of the testis and are the prime source of
the male hormone, testosterone. LH from the pituitary gland regulates Leydig
cell function by the negative feedback loop. The Sertoli cells are highly
specialized cells that maintain the integrity of the seminiferous epithelium
(so that spermatogenesis can occur in an immune privileged area) as well as nourish
the developing sperm.
Approximately
one in 20 men are subfertile, about 85 per cent have suboptimal semen quality, while
azoospermia, coital dysfunction and immune factors contribute to the rest.
Any factors, whether
genetic, physiological, pathological or mechanical, that affect the
spermatogenesis process from the production to time of ejaculation will influence
male fertility.
Causes for male sub fertility
Sperm production problems
|
• Chromosomal or genetic causes
• Undescended testes (failure of the testes to descend at birth) • Infections • Torsion (twisting of the testis in scrotum) • Varicocele (varicose veins of the testes) • Medicines and chemicals • Radiation damage • Unknown cause |
Blockage of sperm transport
|
• Infections
• Prostate-related problems • Absence of vas deferens • Vasectomy |
Sexual problems
(erection and ejaculation problems) |
• Retrograde and premature ejaculation
• Failure of ejaculation • Erectile dysfunction • Infrequent intercourse • Spinal cord injury • Prostate surgery • Damage to nerves • Some medicines |
Hormonal problems
|
• Pituitary tumours
• Congenital lack of LH/FSH (pituitary problem from birth) • Anabolic (androgenic) steroid abuse |
Sperm antibodies
|
• Vasectomy
• Injury or infection in the epididymis • Unknown cause |
Diagnosis
Semen analysis
should be performed after the patientshave abstained from sexual intercourse
for 3–4 days.
Two abnormal
test results are required to diagnose male subfertility. For men with a very
low sperm count or azoospermia, it is important to check their testosterone level (low levels suggest a production impairment) and LH/FSH.
(Hypogonadotrophic hypogonadism is rare and can be treated with FSH and hCG
injections.)
It is also
important to screen for the cystic fibrosis (CF) mutation as a congenital bilateral
absence of the vas deferens (CBAVD) is a minor variant of cystic fibrosis. If
the male partner is found to have the CF mutation, it is important to screen
the female partner for it. If both partners are carriers, there is a one in
four chance of the child being affected by CF and therefore the couple will
require pre-conceptual genetic counselling prior to assisted conception.
Karyotyping is also offered as there may be Y chromosome deletion defects (AZF
region). Specific types of Y chromosome deletion, namely AZFa and AZFb Y
chromosome deletions, carry poor prognosis for surgical
sperm retrieval procedures.
