Testosterone is a naturally occurring steroid hormone responsible for proper growth of sex organs. Its deficiency is marked by a number of physiological and psychological symptoms. Some diseases and injuries can result in low testosterone. Doctors may prescribe hormone replacement therapy to remedy low levels of testosterone.
In mammals, testosterone is produced in the testes of males, in small amounts by female ovaries and in the adrenal glands of both sexes. Testosterone exerts its anabolic (or tissue-building) effects by binding to the androgen receptors in muscle tissue, where it causes cells to increase protein synthesis. It also promotes bone density and increases the production of red blood cells. In males going through puberty, testosterone exhibits androgenic (masculinizing) effects that cause the voice to deepen and the body and face to grow hair.
Low testosterone can occur due to congenital conditions (Klinefelter’s syndrome or Kallmann's syndrome); injuries to the testicles, hypothalamus or pituitary gland; or because of kidney failure and diseases such as both types of diabetes, cirrhosis of the liver, hypertension (high blood pressure), AIDS, sarcoidosis, syphilis, meningitis and mumps.
After age 25, a man’s natural production of testosterone begins to decline at a rate of about 2 percent annually; by age 80, his natural production of testosterone only amounts to 20 percent of peak testosterone levels. Additionally, some medications, chemotherapy and radiation treatments can cause testosterone levels to drop. Alcoholism and chronic stress can cause the body to stop producing normal levels of testosterone.
Men suffering from low testosterone may experience physiological symptoms, including lower libido, thinning skin, erectile dysfunction or impotence, osteoporosis, mild anemia caused by lowered red blood cell counts, chronic fatigue and a decrease in skeletal muscle mass with a concurrent increase in body fat. Low testosterone can also alter blood serum levels of cholesterol and raise levels of bad cholesterol, increasing a man’s risk for high blood pressure, arteriosclerosis and coronary disease. Low testosterone can cause psychological effects such as depression, difficulty concentrating and remembering, and a general decline in mental health accompanied by a poor sense of well-being.
Men who show any of the symptoms of low testosterone should see a doctor. According to Dr. Wayne G. Hellstrom of Tulane University Medical Center, doctors diagnose low testosterone by performing a medical exam, taking a full medical and medication history and testing blood-serum levels of testosterone. A doctor might ask questions about ability to maintain erections, frequency of erections (including nocturnal erections) and frequency of sexual activity or urges to have sex. Doctors may also test bone density and check a patient for changes in body composition.
After ruling out certain congenital conditions and pituitary dysfunction, doctors can prescribe hormone replacement therapy when serum testosterone is low and luteinizing hormone is high. Luteinizing hormone is a precursor to testosterone production.
Testosterone replacement therapy requires patients to take exogenous (externally produced) testosterone to help ease symptoms. Symptoms generally lessen shortly after therapy begins. Treatment can be administered through a variety of methods, including intramuscular injections, transdermal patches, creams or sprays applied to the skin, buccal strips applied to the gums (Striant) and pills. Dosages depend on the type of testosterone and mode of treatment, as some versions last longer in the body and require less frequent administration. Treatment generally is needed throughout a patient's life.
Testosterone therapy can cause a number of side effects. Users may experience masculinizing effects, including acne, oily skin, deepening of the voice, excess growth of facial and/or body hair and fluid retention. Additionally, excess testosterone may cause changes in blood serum cholesterol levels, erectile dysfunction, testicular atrophy, an enlarged prostate and gynecomastia (the development of male breast tissue). Testosterone in pill form has been discouraged for use in men; in high doses, this method of treatment can have adverse effects on the liver.