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).