Harvard Men's Health Watch

Testosterone replacement: A cautionary tale

Every man desires to live long," wrote Jonathan Swift, "but no man would be old." Much has changed over the centuries, but the desire to retain youthful vigor during the golden years has endured. Fortunately, modern medicine has developed a plan for successful aging. It includes getting regular physical activity and mental stimulation; eating right; controlling blood pressure, cholesterol, and blood sugar levels; staying lean; building strong interpersonal relationships; and avoiding tobacco and other risky exposures and activities.

A wise lifestyle can help extend life and slow the aging process — but it takes effort and discipline, especially for gents who have started down the wrong path. So it's no surprise that men continue to look for a medicinal shortcut. One of the most tempting is testosterone.

The manly hormone

Testosterone is the most powerful androgen, a group of steroid hormones whose name is derived from the Greek words for "man-maker." The name is appropriate, since androgens are responsible for the large muscles, strong bones, deep voice, and pattern of hair growth that characterize the gender. The hormone promotes the production of red blood cells. Testosterone also stimulates the growth of the genitals at puberty, and it's responsible for sperm production throughout life. In addition, it has major, if incompletely understood, effects on male behavior; testosterone contributes to energy (and aggressiveness), is essential for the sex drive, and plays a role in normal erections and sexual performance. And after the hormone is converted to dihydrotestosterone, it stimulates the growth of prostate cells and stuns the hair follicles of men genetically predisposed to male pattern baldness.

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