What causes infertility in men?
The most common male infertility factors include azoospermia (no sperm cells are produced) and oligospermia (few sperm cells are produced). Sometimes, sperm cells are malformed or they die before they can reach the egg. In rare cases, infertility in men is caused by a genetic disease such as cystic fibrosis or a chromosomal abnormality.
To be fertile, a man must be able to deliver an adequate quantity of normal sperm to a woman's vagina, and sperm must be able to fertilize the egg. Conditions that interfere with this process can make a man less fertile.
Conditions that increase the temperature of the testes (where sperm are produced) can greatly reduce the number of sperm and the vigor of sperm movement and can increase the number of abnormal sperm. Temperature may be increased by exposure to excessive heat, disorders that produce a prolonged fever, undescended testes (a rare abnormality present at birth), and varicose veins in the testes (varicocele). Certain hormonal or genetic disorders may interfere with sperm production. Hormonal disorders include hyperprolactinemia, hypothyroidism, hypogonadism, and disorders of the adrenal gland (which produces testosterone and other hormones) or pituitary gland (which controls testosterone production). Genetic disorders involve an abnormality of the sex chromosomes, as occurs in Klinefelter syndrome.
Other causes of reduced sperm production include mumps that affect the testes (mumps orchitis), injury to the testes, exposure to industrial or environmental toxins, and drugs. Drugs include androgens (such as testosterone), aspirin when taken for a long time, chlorambucil, colchicine, corticosteroids (such as prednisone), cotrimoxazole, cyclophosphamide, drugs used to treat malaria, estrogens taken to treat prostate cancer, marijuana, medroxyprogesterone, methotrexate, monoamine oxidase inhibitors (MAOIs—a type of antidepressant), nicotine, nitrofurantoin, opioids (narcotics), spironolactone, and sulfasalazine. Use of anabolic steroids may affect hormone levels and thus also interfere with sperm production. Excessive consumption of alcohol may reduce sperm production.
Some disorders result in the complete absence of sperm (azoospermia) in semen. They include serious disorders of the testes and blocked or missing vasa deferentia, missing seminal vesicles, and blockage of both ejaculatory ducts. Occasionally, semen, which contains the sperm, moves in the wrong direction. This disorder, called retrograde ejaculation, is more common among men who have diabetes or who have had pelvic surgery, such as prostate removal. Infertility may result.
In addition, use of lubricants, timing and frequency of intercourse, use of medications or recreational drugs, exposure to chemicals or radiation, smoking and use of steroids can affect fertility in a man.