Hormonal Abnormalities

Low levels of testosterone from any cause may result in defective sperm production. Hypogonadism is a severe deficiency in gonadotropin–releasing hormone (GnRH). It is usually present at the time of birth, although it can develop later in life from tumors of the pituitary gland, other brain tumors, or radiation treatments. In rare cases, it can develop without any apparent cause after puberty. In such cases, it may be brought on by excessive exercise, malnutrition, or illness. Genetic causes of pituitary gland malfunctions can prevent production of reproductive hormones, but such conditions are very rare contributors to male infertility. They include a disorder known as selective deficiency of FSH and LH, hypogonadism, Kallman’s syndrome, and panhypopituitarism (in which the pituitary gland fails to make almost all hormones). In some cases, Leydig cells are defective and unable to respond to testosterone.

Other Causes of Infertility

The same conditions that cause retrograde ejaculation (e.g.., diabetes, multiple sclerosis, bladder neck or prostate surgery, and spinal cord injury) may also be responsible for failure to ejaculate. Chronic prostatitis (inflammation of the prostrate gland) can also cause sperm motility problems. Abnormalities of the thyroid or adrenal glands may have an indirect effect on fertility. Other medical conditions that can affect male fertility include any severe injury or major surgery, heart attack, liver failure, chronic anemia, kidney failure, obesity, or starvation.

Drugs and Medications

The effects of medications on sperm quality and count have not been rigorously studied, and many medicines are commonly prescribed without knowing whether they impair fertility. Anabolic steroids are known to severely impair sperm production. Cocaine or heavy marijuana use appears to temporarily reduce the number and quality of sperm by as much as 50%. Sperm actually have receptors for certain compounds in marijuana that resemble natural substances and which may impair the sperm’s ability to swim and may also inhibit their ability to penetrate the egg.

Sexual Problems

In less than 1% of males with infertility problems, a problem with sexual intercourse or technique will affect fertility. Impotence, premature ejaculation, dyspareunia (painful intercourse), or psychological or relationship problems can contribute to infertility, although these conditions are usually very treatable.

Lifestyle Factors

Stress may interfere with the hormone GnRH and reduce sperm counts. Smoking impairs sperm motility, reduces sperm lifespan, and may cause genetic changes that affect the offspring. (Alcohol does not appear to affect fertility unless it is so abused that it has caused liver changes.) Obesity and excessive endurance exercise may also reduce sperm production, but losing weight and reducing exercise levels can reverse the problem. Low levels of dietary selenium and zinc, which are necessary for the formation and maturation of sperm, are associated with an increased risk of infertility. Some experts believe that vitamin C deficiency causes the sperm to clump together (agglutinate), which impairs movement. Frequent intercourse was suspected for awhile of reducing fertility because of the time required to replenish sperm, but this is unproved. A number of studies have found no negative effects on fertility from wearing tight trousers, briefs, or athletic supports, even every day. Men are at risk for infertility, however, only when the testes are exposed for prolonged periods to internal body temperatures, which occurs only rarely, such as in men with undescended testicles.