The most common cause of male infertility is low sperm count. The absence of sperm in the semen is less common, affecting 1 out of 100 men and affecting 10 to 15 out of 100 infertile men.
Causes of sperm count problems include:
- Hormonal problems in the testicles or pituitary gland. The pituitary gland releases hormones that stimulate the testicles to produce testosterone.
- Testicular injury or failure, either present at birth (congenital) or associated with radiation or toxic chemical exposure.
- Cancer treatment with certain kinds of chemotherapy or radiation.
- Antibodies that attack sperm and that also may be present in semen. Sperm antibodies sometimes develop when a man’s sperm has been exposed to his immune system (outside of the testicles). This may happen after a vasectomy, an infection, or an injury to the testicles.
- Drug use (some prescription medicines, and marijuana and tobacco use).
- Structural problems. These include:
- A varicocele in the testicles.
- Blocked ejaculation due to a surgical vasectomy.
- Absence of a vas deferens (a birth defect that may be associated with the cystic fibrosis genes).
- Retrograde ejaculation (the ejaculation of semen into the bladder rather than out through the penis).
- Chromosomal problems (such as Klinefelter syndrome).
- Genetic problems.