the inability to conceive (reproduce) after at least one year of unprotected
intercourse. Since most people are able to conceive within this time,
physicians recommend that couples unable to do so be assessed for fertility
problems. In men, hormone disorders, illness, reproductive anatomy trauma
and obstruction, and sexual dysfunction can temporarily or permanently
affect sperm and prevent conception. Some disorders become more difficult to
treat the longer they persist without treatment.
Sperm development (spermatogenesis) takes place in the
seminiferous tubules (ducts) of the testes. Cell division produces
spermatozoa (mature sperm cells) that contain one-half of a man's genetic
code. Each spermatogenesis cycle consists of six stages and takes about 16
days to complete. Approximately five cycles, or 2 ½ months, are needed to
produce one mature sperm. Mitochondria (energy-generating organelles) inside
each sperm power its tail (flagellum) so that it can swim to the female egg
once inside the vagina. Sperm development is ultimately controlled by the
endocrine (hormonal) system that comprises the
Because sperm development takes over 2 months, illness that was present
during the first cycle may affect mature sperm, regardless of a man's health
at the time of examination.
Incidence and Prevalence
According to the National Institutes of Health, male infertility is involved
in approximately 40% of the 2.6 million infertile married couples in the
United States. One-half of these men experience irreversible infertility and
cannot father children, and a small number of these cases are caused by a
treatable medical condition.
Causes and Risk Factors
The primary causes of male infertility are problems with sperm production
or delivery. Impaired production or delivery may result from hormonal
dysfunction, trauma or defect in the reproductive system, and illness:
- Cryptorchidism (failure of testes to descend; can impair
fibrosis (may cause absence of sperm, vas deferens, or seminal
- Ductal obstruction (caused by repeated infection, inflammation, or
- Hemochromatosis (metabolic disorder; causes iron deposition in the
- Hormone dysfunction (caused by disorder in the
- Retrograde ejaculation
- Sexually transmitted diseases (STDs;
cause obstruction, infection, and scarring)
- Sickle cell anemia (can cause
- Systemic disease (fever, infection, kidney disease, metabolic
disorder; can impair spermatogenesis)
- Testicular trauma (damage to testes)
Certain drugs used to treat hypertension, arthritis, and digestive
disease, as well as chemotherapy drugs are associated with sperm production
problems and infertility.
Retrograde ejaculation occurs when impairment of the muscles or
nerves of the bladder neck prohibit it from closing during ejaculation,
allowing semen to flow backwards into the bladder. It may result from
bladder surgery, a developmental defect in the urethra or bladder, or
disease that affects the nervous system, including
diabetes. Diminished or "dry" ejaculation and cloudy urine after
ejaculation may be signs of this condition.
Inflammatory infections of the prostate (prostatitis), epididymis
(epididymitis), and testicles (orchitis), can cause irreversible infertility
if they occur before puberty.
Testicular trauma, resulting from injury, surgery, or infection
can trigger an immune response in the testes that may damage sperm. Though
their effects are not fully understood, antibodies can impair a sperm cell's
ability to swim through cervical mucus or to penetrate a female egg.