What is the main reason for male infertility?

The most frequent cause of male infertility is a defect in sperm production (spermatogenesis), resulting in seminograms with low sperm count or low sperm motility. This is the problem in 65-80% of men who present with difficulties in achieving pregnancy.

This is due to a failure at the testicular level, and in the vast majority of cases we are not able to find a cause for it. In a smaller percentage of cases we can explain this failure by:

• Genetic abnormalities, such as microdeletions in the Y chromosome or Klinefelter syndrome.
• Cryptorchidism: damage to spermatogenesis in pacients with a history of undescended testicle(s) is related to genetic and hormonal causes, that can be partially reversible with a early surgical intervention to descend the testicles.
• Alterationes in the hormone receptors for testosterone, estrogen or FSH.
• Diseases such as myotonic dystrophy.
• Varicocele, although in the vast majority of cases these patients will have normal seminograms (normozoospermia).
• Testicular infections due to mumps, STDs such as chlamydia, gonococcus or HIV.
• Chemotherapy or radiotherapy
• Environmental pollution
• Smoking

Other less frequent causes of male infertility include:

• Idiopathic male infertility: men who, in spite of presenting normal seminograms, do not achieve pregnancy (10-20%).
• Obstructive azoospermia (5%): In these patients, the production of spermatozoa at the testicular level is normal, but the ducts that should allow the exit of these spermatozoa into the ejaculate are blocked. This can occur due to infections or genetic alterations (such as cystic fibrosis) etc.
• Endocrine disorders (2-5%): a failure at the cerebral level can produce hypogonadism, and the testicle does not receive the correct signals to carry out correct spermatogenesis. This can be due to congenital alterations, tumors, drug use such as opioids or cannabis, obesity or serious systemic diseases.