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The Lowdown on Bulking Up

Highlights the popularity of androstenedione (andro) in the United States since the admission made by Major League player Mark McGwire that he is taking the steroid hormone. Functions of andro; Composition of andro.

Ever since Major League slugger Mark McGwire admitted to taking the hormone androstenedione, sales of the supplement have soared like his record-breaking home runs. No question: the use of andro is legal. But is it safe?

Manufactured by the gonads and the adrenal gland, andro is a steroid hormone, the biochemical precursor to testosterone. Athletes take it because it speeds muscle recovery so lean muscle mass can develop faster. However, there are virtually no studies on how andro works or what its side effects might be, warns Gary Wadler, M.D., an associate professor of medicine at New York University. "People assume that andro isn't harmful," he says. "But nobody has really looked at its anabolic capabilities."

What we know about other steroid hormones should give andro users pause. Because the body converts testosterone to estrogen, men on anabolic steroids, which derive from testosterone, may feminize as they get stronger, developing high-pitched voices, shrinking testicles and enlarged breast tissue. Women popping steroids may notice breast atrophy, deepening voice and male pattern baldness. Steroids can also stunt growth in teenagers by closing their growth plates. Steroid users also run the risk of liver tumors, surging cholesterol levels and behavioral changes ranging from mere assertiveness to the infamous 'roids rage. "Andro is related to testosterone, so there's little reason to doubt that their effects are similar," says Wadler.

A safer bet, and one used by many athletes, including McGwire, is the supplement creatine. Composed of three amino acids produced by the liver and kidneys, creatine is found in meat and fish. Like andro, it builds strength, but doesn't alter hormone levels. And while Wadler doesn't recommend use of dietary supplements to bulk up, he does note that a "large body of good literature" highlights creatine as an effective energy source that boosts body mass and performance in high-intensity, low-duration exercises involving spurts of speed and power, like weightlifting, sprinting or batting.

PHOTO (COLOR): Major League slugger Mark McGwire