Testosterone, a steroid hormone that plays a major role in male development and sexual behavior, is produced by the testicles in response to stimulation by the pituitary gland. A low testosterone level, otherwise known as hypogonadism, can result from problems with the testicles themselves or from deficiencies in pituitary hormones. The signs and symptoms of male hypogonadism are dictated by the age at which the condition develops.
Congenital Hypogonadism
When a genetically male fetus is not exposed to sufficient levels of testosterone, normal development of the penis and scrotum is either completely interrupted or delayed. According to "The Merck Manual of Diagnosis and Therapy," if testosterone is completely absent during the pregnancy, the infant is born with what appear to be normal external female genitalia. Partial testosterone deficiency results in malformed or abnormally small external male genitalia or undescended testes.
Childhood-Onset Hypogonadism
Prepubescent males who develop testosterone deficiency typically do not exhibit any symptoms until adolescence, when a diagnosis of delayed puberty reveals the condition. If hypogonadism is unrecognized during adolescence, sexual development is interrupted. Untreated males fail to develop body hair, their voices do not deepen, their musculature remains immature and normal growth of the genitalia is delayed.
Adult-Onset Hypogonadism
Testosterone levels normally fall with aging, but pituitary or testicular failure during adulthood will cause significant testosterone deficiency. Testicular failure can result from infections such as mumps, alcohol abuse, radiation therapy, chemotherapy or high doses of certain drugs such as cimetidine or spironolactone. Pituitary failure has a multitude of potential causes, including trauma, tumors, infections and substance abuse. A 2004 review in "The Journal of Clinical Endocrinology and Metabolism" reports that hypogonadism occurs relatively frequently in men with type 2 diabetes, metabolic syndrome, obesity, cardiovascular disease or other chronic diseases. Symptoms of adult-onset hypogonadism vary with the duration of the testosterone deficiency and include decreased libido, low sperm count, erectile dysfunction, decreased muscle mass, increased body fat, loss of body hair, development of breast tissue, decreased testicular size, sleep disturbances and mood changes, such as anger, irritability or depression.
Considerations
Because many of the symptoms of adult-onset hypogonadism overlap with those of other conditions, it is important to get a proper diagnosis. Treatment for hypogonadism entails replacement of testosterone to achieve normal levels, and inappropriate testosterone administration can cause significant side effects. Check with your doctor if you are concerned about low testosterone levels.
References
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Male Hypogonadism"; Mark H. Beers, M.D., Editor-In-Chief; 2006
- "The Journal of Clinical Endocrinology and Metabolism"; Frequent occurrence of hypogonadotropic hypogonadism in type 2 diabetes; Dhindsa S, et al.; 2004
