Causes of infertility in men

Abnormal sperm production

Oligospermia means a sperm concentration below reference values; azoospermia means no sperm in the ejaculate. Possible causes are hormonal, genetic, obstructive, infectious, or linked to a medical history such as an undescended testicle, chemotherapy or radiotherapy.

These parameters are measured by a semen analysis, ordered and interpreted by a doctor. A single isolated result is not enough to conclude anything.

Abnormal motility and morphology

Asthenospermia means sperm move too poorly; teratospermia means a high proportion of abnormally shaped sperm. Both can coexist with a normal concentration and still hinder fertilisation.

Varicocele

A varicocele is a dilation of the veins of the spermatic cord. It is common, and in some cases is associated with poorer semen parameters, probably through raised testicular temperature and oxidative stress. Whether to treat it is decided case by case.

Modifiable exposure factors

Sperm production is sensitive to heat and renews itself over a few months, which makes some exposures potentially reversible. Smoking and alcohol are the best documented. Testicular heat is plausible and studied; the effect of mobile phone radiation remains emerging and debated. Each linked sheet states its level of evidence.