Doctors administer injections of synthetic versions of the natural hormone testosterone to treat low production of testosterone. These injections are not appropriate for patients with certain pre-existing medical conditions and may cause a number of detrimental side effects and complications.
Testosterone occurs naturally in mammals and is produced in the testes of males, also the site of sperm production; in much smaller amounts by female ovaries; and by the adrenal glands of both sexes. Testosterone causes both anabolic, tissue building, and androgenic, masculinising, effects. By binding to the androgen receptors in muscle tissues, testosterone promotes muscle growth and bone density. In pubertal males, testosterone causes the development of male sexual characteristics, including a deepened voice and facial hair.
Pharmaceutical companies offer a number of synthetic versions of testosterone that differ from the natural hormone only by modifications that extend the drug's effects. Injectable versions include testosterone cypionate and testosterone enanthate.
Testosterone injections are prescribed for use in men suffering from hypogonadism, a condition in which the body does not produce enough of the hormone naturally. Hypogonadism can result from congenital conditions (such as Klinefelter's syndrome), injuries or trauma to the hypothalamus or pituitary, chemotherapy or diseases such as alcoholism, hepatitis, diabetes and syphilis.
Doctors may also prescribe testosterone to men as part of a regimen of hormone-replacement therapy. After age 25, a man's natural production of testosterone declines at a rate of about 2 per cent yearly, and testosterone injections can help supplement this age-related deficit.
Hypogonadism can cause men to experience a decrease in muscle mass and bone density, loss of energy, decreased libido, difficulty remembering and concentrating, fatigue, erectile dysfunction and a decline in overall mental health and well-being. Doctors use injectable testosterone during hormone-replacement therapy to alleviate or reverse these effects and improve the quality of life in men as they age.
According to Tulane University Medical Center's Dr. Wayne Hellstrom, testosterone administration should try to replicate an individual's natural production of testosterone, and the dosage for injectable testosterone can range from 200 to 300 mg, every two or three weeks.
Because testosterone can enlarge the prostate, testosterone injections are not advised for men suffering from prostate cancer and for men with male breast cancer. Additionally, drugs.com reports that men who have a history of heart, liver or circulatory disease should avoid taking testosterone injections and that diabetic patients may have to adjust their insulin dosages, as testosterone can alter blood-sugar levels.
Testosterone can cause a number of side effects, the most serious of which is peliosis hepatitis, a sometimes fatal condition in which blood-filled cysts form inside the liver and/or spleen. As testosterone can also alter blood serum cholesterol levels, patients may also suffer from arteriosclerosis, clotting problems, stroke and congestive heart failure.
Some patients have reported allergic reactions to testosterone, which drugs.com lists as including hives, rash, laboured breathing, chest pain and swelling of the face and mouth.
Excess testosterone can also cause masculinising effects such as hirsutism (excess body hair), male pattern baldness, altered libido, acne and oily skin. Users may also suffer from gynaecomastia (male breasts) and erectile dysfunction.
Frequent injections of testosterone can inconvenience patients and may cause injection-site complications such as abscesses, infection and the build-up of scar tissue. Additionally, Dr. Hellstrom points out that while testosterone injections are safe, injectable versions of testosterone can cause fluctuations in energy, mood and libido.