BOSTON, April 1 2004-- Millions of men are turning to testosterone therapy in hopes of restoring vitality and slowing the aging process. Boosting testosterone makes sense for men with low hormone levels. But for men with normal levels, little is known about the long-term effects of testosterone therapy on the heart, blood vessels, and other parts of the body.

By age 60, about one in five men have testosterone levels lower than the norm. Millions of men are turning to testosterone therapy in hopes of restoring vitality and slowing the aging process.

According to the April Harvard Heart Letter, there is still much to be discovered about the effects of testosterone therapy on men's health. One gray area is how daily doses of the hormone affect the heart, blood vessels, and circulation. Some studies suggest that testosterone can lower blood pressure, increase levels of HDL (good) cholesterol, and decrease the chances of developing atherosclerosis or diabetes. If this paints a positive, why-not- start-today picture of testosterone therapy, the recent flip-flop on postmenopausal hormone therapy in women should raise a red flag.

According to the Harvard Heart Letter editors, men shouldn't be taking testosterone unless their bodies aren't making enough of the hormone. Tip-offs include fatigue, muscle weakness, dwindling interest in sex, osteoporosis, or a suspicious bone fracture. Men whose testosterone levels are in the normal range should approach hormone therapy as an experimental treatment, aware of both the possible benefits and potential harm, until more is known about its long-term effects.

The Harvard Heart Letter is available from Harvard Health Publications, the publishing division of the Harvard Medical School. You can subscribe to the Harvard Heart Letter for $32 per year at http://www.health.harvard.edu/