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Benefits and risks

There’s pretty good evidence that testosterone treatment will make a man leaner, though not necessarily stronger. Citing 12 placebo-controlled studies of body composition, the IOM reported that testosterone treatment probably does increase lean-body mass and decrease fat. But surprisingly, muscle strength showed no improvement in 8 of 10 studies. Results on mood and cognition are too mixed to draw any firm conclusions. Some researchers see a positive trend in bone density.

As for sex, no surprise — testosterone plays an important role in sexual interest and motivation. Some research hints at a use-it-or-lose-it feedback loop — testosterone levels increase with sexual stimulation and activity, and decline after long periods of celibacy. But even men with low levels of the hormone can have erections.

Testosterone therapy hasn’t been effective as a treatment for erectile dysfunction. In younger men it shrinks the testes and in all men, drops the sperm count. Yet doctors who prescribe testosterone say their patients often report that it improves the quality of their erections.

On the risk side, one of the big worries has been heart attacks and other cardiovascular problems. But research has chipped away at that idea. Low, not high, testosterone has been linked to cardiovascular risks like diabetes. Testosterone treatment does not have an appreciable effect on cholesterol. In clinical studies, treatment has been shown to widen coronary arteries and may even help angina. Red blood cell counts sometimes go up, although this is more common with injections of the hormone. For men with anemia, that side effect could be a plus. But higher red blood cell counts can also make the blood thicker and therefore more likely to clot. So doctors who prescribe testosterone should be careful about monitoring red blood cell counts.

The other big worry is prostate cancer. Testosterone doesn’t seem to initiate it. In fact, there’s reason to believe that in men with naturally high levels, the hormone may act as a prostate cancer inhibitor. On the other hand, it’s pretty clear that once prostate cancer is present, the cancerous cells need testosterone and related hormones to grow. About half of all men over age 50 harbor cancer cells in their prostate that aren’t causing symptoms or doing any real harm. Theoretically at least, testosterone treatment might “wake up” those cells and make them aggressively cancerous. To guard against that, some doctors insist on a prostate biopsy to rule out the presence of cancer before they start a man on testosterone therapy.
health.harvard.edu/newsweek/Hormone-replacement-the-male-version.htm