The second drawback is biology itself. No hormone can turn back time. Despite some of the marketing claims--"scientists have proven that 10 to 20 years of aging can be reversed in less than a year," reads one doctor's Internet site--there's no evidence that HRT has extended anyone's life by a single day. Injections of growth hormone often make people look and feel fitter, for instance, but they don't seem to be any stronger. Only weight training can do that, and there's no evidence that taking HGH even enhances muscles' response to pumping iron.
The reputation of DHEA as an anti-aging elixir rests largely on a study released by UC San Diego researchers six years ago, in which investigators trumpeted large boosts in feelings of well-being for healthy older men and women taking DHEA pills. Many endocrinologists were skeptical at the time, and indeed a longer-term 1999 trial found no such lifts in mood from DHEA.
As for melatonin, its mildly sedating effects are barely distinguishable from those of a sugar pill, endocrinologists say.
The most promising of these hormones may be testosterone. Older men taking it quickly recover sexual potency, a leaner body, and, with exercise, become stronger than they may have without the hormone. But investigators still don't know enough to say whether these benefits translate into a longer life or even a significantly healthier one.
Finally, HRT's long-term risks are a wild card. This may not bother an 80-year-old who's trying to buy a few more good years. But it's very relevant to a healthy 50-year-old who might have 20, 30 even 40 years left.
"I'm not worried about DHEA and melatonin--they're pretty innocuous," says Lawrence Frohman, a hormone researcher at the University of Illinois, Chicago. "But growth hormone and testosterone are potent hormones, and the potential for long-term problems is very real." The big knock against testosterone is its link to prostate cancer: The hormone could accelerate the growth of prostate tumors.
"Certainly there's the possibility that testosterone could make a slow-growing cancer more aggressive," says Ronald Swerdloff, chief of the division of endocrinology at the Harbor-UCLA Medical School.
Side effects of HGH treatment include carpal tunnel syndrome, diabetes, and pooling of fluids in the skin that, over time, may lead to high blood pressure and heart failure.
"Some of these effects are reversible if you bring down the dosage," says Paul Fitzgerald, a clinical endocrinologist at UC San Francisco, "but there's a group of people out there who will go to any lengths to look younger, take any risk, and who will escalate to very high doses."
A Troubling Dearth of Treatment Standards
The unknowns might be less worrisome if anti-aging doctors were predominantly endocrinologists with proven clinical records. They aren't. The A4M does conduct a certification exam, requiring at least five years' experience treating patients and 200 hours of study, with a strong emphasis on the endocrine system. Though not recognized as a specialty by the American Board of Medical Specialties, anti-aging certification at least establishes standards for treatment and dosage. Yet most A4M members are not board certified.
"We have some very good people," says Klatz, A4M's president. "But like any profession, there are people with checkered pasts."
This is one reason why mainstream academic researchers, along with scientists at the National Institute on Aging, have been skeptical of anti-aging practitioners; such a lucrative opportunity, they suspect, very likely has attracted doctors who are prescribing hormones carelessly.
"Allow me to put it this way," says Thomas Perls, director of the New England Centenarian Study and chief of gerontology at Beth Israel and Deaconess Medical Center in Boston. "I think these anti-aging guys are hucksters and snake oil salesmen. They paint a very grim picture of old age that just does not match the reality. . . . The retirement years can be a most wonderful time of life, if you take care of yourself, exercise and watch your diet. I wonder how much these anti-aging doctors really understand about aging."
Many anti-aging doctors, for example, determine a client's HGH level by taking a single blood sample and sending it to a lab to be tested for something called IGF-I. Growth hormone naturally stimulates production of IGF-I, and low levels of one usually reflect low levels of the other. Usually--but not always.
"The IGF-I test is not a reliable test for growth hormone," Fitzgerald says. "A person's blood may show very low levels of IGF-I, yet they are still able to produce significant amounts of HGH. We see it all the time."