Keep Testosterone In Balance

Produced by the testes (though women's ovaries make some, too), the hormone propels prepubescent boys toward deeper voices and hairy chests. In a grown man, it fuels a healthy libido, builds muscle mass and helps maintain energy levels. But too much of it -- or too little -- can wreak havoc on a man's behavior and physique.

Why More Isn't Always Better

According to a study in the April 1999 Journal of Behavioral Medicine, higher-than-average testosterone levels offer certain benefits but also carry some serious risks. Researchers at Pennsylvania State University in University Park, Penn., reviewed the records of 4,393 men between the ages of 32 and 44 who had served in the military between 1965 and 1971. Their blood had been drawn to determine testosterone levels -- which ranged from 53 to 1,500 nanograms per deciliter, with an average of 679. (The normal range in males is 270 to 1,070 nanograms.)

Men whose testosterone levels were slightly above average were 45% less likely to have high blood pressure, 72% less likely to have experienced a heart attack and 75% less likely to be obese than men whose levels were slightly below average. These men were also 45% less likely to rate their own health as fair or poor.

But the results weren't all rosy. These men were also 24% more likely to report one or more injuries, 32% more likely to consume five or more drinks in a day, 35% more likely to have had a sexually transmitted infection, and 151% more likely to smoke.

The news got worse at very high testosterone levels (1000 nanograms), where men were even more likely to engage in risky behavior -- and less likely to reap the positive health benefits of testosterone.

The results aren't really surprising, says lead author Alan Booth, PhD -- a professor of sociology and human development -- because testosterone has been associated with risky behavior in many studies. Men with high testosterone levels are more likely to be involved in criminal activity and antisocial behavior, get in trouble in school, remain single, and be unemployed.

But this doesn't mean that all men with high testosterone levels are doomed to a bad fate, he said. "There's lots of high testosterone people out there with good marriages who don't commit crimes."

Taking all the factors together, researchers found that the healthiest men overall had testosterone levels between 400 to 600 nanograms. They seemed to enjoy the most benefits and experience the least risks associated with the hormone.

When Medical Treatment Is Needed

Some men may have higher testosterone levels than others, but it's rare that a man's level is so high that he needs treatment, says Eugene R. Shippen, MD, author of The Testosterone Syndrome. It's much more common, he says, to treat low testosterone levels.