There are a number of causes for male infertility, but they all affect quantity and/or quality of sperm. These causes include:
- The sperm's exit route is blocked (from birth, by scarring from infection, past vasectomy, etc.)
- Retrograde ejaculate (semen is ejaculated backwards, into the bladder)
- Sperm production in the testes is low or absent (there can be many causes for this finding)
Low sperm count
Low sperm count, also called oligospermia, is the most common cause of male infertility. Complete lack of sperm, called azoospermia, is much less common, affecting less than 1% of the population. Low sperm count is diagnosed when the number of sperm falls below 20 million in a milliliter of semen. (Normal range is between 20 million and 120 million per milliliter of semen.) When sperm count is too low, sperm has a much lower chance of reaching and fertilizing the egg, leading to infertility.
As the list above shows, many possible causes of low sperm count exist. Some are structural: even when sperm is produced normally in the testes, an obstruction in the ejaculation tract may block the sperm. Other causes include hormonal insufficiency, testicular injuries and chromosomal/genetic abnormalities (such as Klinefelter syndrome). In addition, vasectomy can be considered a cause of male infertility, if the male partner changes his mind about having children after having had a vasectomy.
One of the most common factors leading to decreased sperm count is varicocele. This is when the veins in the scrotum (the skin "sack" that contains the testicles) are dilated on one or both sides. This heats the inside of the scrotum excessively and may affect sperm production. Other factors can also include a blockage in a man's reproductive system, retrograde ejaculate and certain medications.
Azoospermia is a condition in which the man has no sperm in the ejaculate. Families often assume that a diagnosis of azoospermia rules out the possibility of having a child. However, with the treatments available today, that is not necessary the case. There are now methods that can harvest even small amounts of sperm that are produced in the testes as a result of interventions, and CHR’s affiliate urologists can perform these micro-surgeries to help azoospermic men become fathers.
Norbert Gleicher, MD, leads CHR’s clinical and research efforts as Medical Director and Chief Scientist. A world-renowned specialist in reproductive endocrinology, Dr. Gleicher has published hundreds of peer-reviewed papers and lectured globally while keeping an active clinical career focused on ovarian aging, immunological issues and other difficult cases of infertility.