Are You Man Enough?

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But testosterone is at issue in larger debates about behavioral differences between men and women and which differences are biologically determined. A few Sundays ago, the New York Times Magazine ran a long piece by Andrew Sullivan, 36, the former editor of the New Republic, in which he reported his own experience with testosterone therapy. In two years he has gained 20 lbs. of muscle. And in the days right after his once-every-two-weeks shot, he reports feeling lustier, more energetic, more confident and more quarrelsome--more potent, in all senses of the word.

Looking over the scientific research on testosterone, Sullivan speculated on the extent to which such traits as aggression, competitiveness and risk taking, things we still think of as male behavior, are linked to the fact that men's bodies produce far more testosterone than women's bodies. His answer--a lot--was offered more as an intuition than a conclusion, but it produced a spate of fang baring among some higher primates in the media and scientific world, since it implies that gender differences owe more to biology than many people would like to believe. Three researchers wrote the Times to complain that Sullivan had overstated their thinking. In the online magazine Slate, columnist Judith Shulevitz attacked Sullivan for favoring nature over environment in a debate in which nobody knows yet which is which. In the days that followed, Sullivan fired back at Shulevitz in Slate, she attacked again, and other writers joined in. If testosterone use becomes a true cultural phenomenon, expect the conversations about its role in gender differences to become even more, well, aggressive.

So just what does testosterone actually do for you? And to you? And how does it figure among the physical and environmental pressures that account for head-banging aggression, or even just the trading pit on Wall Street? One reason testosterone enjoys a near mythical status is that myth is what takes over when conclusive data are scarce. Though testosterone was first isolated in 1935, hormone-replacement therapy is one of the few areas of medicine where research on men lags behind that on women.

What we do know is that testosterone is an androgen, as the family of male sex hormones are called, and these hormones, in turn, are made up of the fat known as steroids. Both men and women produce testosterone in their bodies, men in the testes and adrenal glands, women in the adrenal glands and ovaries. But men produce much more--the average healthy male has 260 to 1,000 nanograms of testosterone per deciliter of blood plasma. For women the range is 15 to 70. But because men differ on how effectively their bodies process the substance--for instance, some have more receptors around their body that absorb it--a man on the low end of the normal range can still have all the testosterone he needs for normal sex drive and other benefits. In healthy men, levels also vary during the day, peaking around 8 a.m., which is why men commonly awaken in a state of sexual arousal, and dropping as much as half before bedtime.