The most common cause of male infertility is low sperm count. Absence of sperm in the semen is less common, affecting only one percent of all men and 10 to 15 percent of 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, which 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 injury to the testicles.
- Drug use (some prescription medications, 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's syndrome).
Male Reproductive System
The male reproductive system consists of the penis, two testicles, two epididymides, two vas deferentia, two seminal vesicles, and the prostate gland.
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Primary Medical Reviewer
Joy Melnikow, MD, MPH
Specialist Medical Reviewer
Kirtly Jones, MD
Obstetrics and Gynecology