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Infertility: Problems With the Man's Reproductive System

Topic Overview

The most common cause of male infertility is low sperm count. 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.footnote 1

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.footnote 2
  • 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.

See a picture of the male reproductive system.

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