Testosterone

Testosterone levels decrease with aging because of failure of the hypothalamus or pituitary to produce enough gonadotropins (secondary hypogonadism) and, to some extent, because of failure of the testes to produce enough testosterone in response to gonadotropins (primary hypogonadism). About 5% of men aged 50 and 70% of men aged 70 are hypogonadal, resulting in a symptom complex of reduced muscle mass, strength, and cognitive function. Low testosterone levels increase risk of coronary artery disease in elderly men.

Testosterone therapy may benefit men with documented low levels. Typical forms and dosages include 30 mg of a mucoadhesive applied every 12 h to the buccal mucosa, 200 mg IM of testosterone enanthate or testosterone cypionate given every 10 to 14 days, 5 to 10 g of testosterone gel applied to skin of the upper body once/day, and a 5-mg testosterone patch applied once/day. Testosterone gel maintains physiologic blood levels more consistently than other forms, but all forms are efficacious. Patches may cause skin rashes.

In elderly men, testosterone therapy increases libido, muscle strength and mass, bone density, and visuospatial cognitive performance; it decreases leptin levels and usually improves mood. Coronary artery vasodilation is increased through release of nitric oxide; cardiac electrophysiologic function may improve in elderly men with coronary artery disease. Testosterone therapy may attenuate erectile dysfunction and appears to have no deleterious effects on lipid levels.

Testosterone therapy stimulates erythropoietin secretion and increases Hct, sometimes to levels > 55%, which increase risk of stroke. This increase (polycythemia) does not depend on the baseline erythropoietin level, testosterone dose, or duration of therapy. Hct should be checked every 6 to 12 mo. If Hct is >= 54%, reducing the testosterone dose by ¼ or 1/3 may help. In some patients, especially those who are obese or who have a chronic pulmonary disorder, testosterone therapy can aggravate sleep apnea.

Testosterone therapy can increase prostate-specific antigen (PSA). The increase is usually only 10 to 30% and to levels within the age-adjusted normal range, but levels may increase by 100% without evidence of prostate cancer. Therapy probably does not cause prostate cancer but may enhance growth of existing prostate cancer. If PSA levels are elevated or borderline before treatment, prostate cancer should usually be ruled out before testosterone therapy is begun. However, for many men, even some with recognized prostate cancer, benefits outweigh risks; thus, after careful consideration, therapy may be appropriate, but close monitoring is necessary. Testosterone therapy rarely causes prostatic obstructive symptoms even if PSA levels increase. Men who take testosterone therapy should have a digital rectal examination and serum PSA testing 3 mo after beginning therapy and annually thereafter.

The effects of testosterone therapy on longevity are unknown.

This topic was last updated March 2006.