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Winter/Spring 2004 Vol. 4 No. 1



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©Alberto Ruggieri/The Image Bank

Testosterone
and Aging

Men's 'Fountain of Youth' Drug
Needs More Study

Fatigued? Depressed? Flagging libido? Is a testosterone boost all you need? Hundreds of thousands of men think so, as the rapidly rising number of testosterone therapy prescriptions written each year attests.









Despite its popularity, testosterone therapy has not been officially approved to treat conditions associated with decreasing levels of the hormone in aging men. Moreover, it has not been rigorously studied to determine if it can have these positive effects without triggering health problems.

A proposed large-scale clinical study of testosterone therapy for treating age-related conditions in older men was put on hold in 2002 until a committee of the Institute of Medicine could assess what is known about the therapy's benefits and risks and offer its guidance on the best way to proceed with such studies.

The verdict? "We really don't know much at all about normal levels of testosterone at different ages, how decreased testosterone levels affect men's health, and whether this therapy might increase the risk of prostate cancer or other health problems," said committee chair Dan Blazer, professor of psychiatry and behavioral sciences, Duke University Medical Center, Durham, N.C. "There have been only 31 randomized clinical trials of testosterone therapy in men ages 65 and older, and just one lasted longer than a year. Those studies simply have not provided enough evidence for men and their physicians to feel certain that the therapy really works and is safe."

Molecular model of testosterone, ©Alfred Pasieka/Science Photo Library

The report proposes a stepwise approach to conducting the clinical studies needed to ascertain the risks and benefits. The first step should be to firmly establish the therapy's effectiveness in treating age-related conditions, which can be done with smaller trials. The committee estimated that several hundred older men would need to be monitored for one to two years. If clear efficacy is demonstrated in the initial studies, then the next step should be a large-scale trial involving several thousand men followed over a longer time frame.

The trials should involve only older men -- that is, 65 and older -- who have clinically low testosterone levels and at least one symptom that might be related to low testosterone. This is the population most likely to benefit from the therapy. The committee acknowledged that the majority of testosterone users are middle-aged men seeking to pre-empt the effects of aging. However, it did not recommend studies focused on this age group because prostate cancer is a slow-growing and often latent disease and the death rate is lower in those under 65, so clinical trials to assess the risks for this population would have to be much larger and last many more years than those focused on older men.

Moreover, the committee discouraged healthy men from using the therapy as a means of trying to prevent possible future health conditions or to boost strength or mood, at least while the jury is still out on the risks and benefits. "For men whose testosterone is in the normal range, there is no proof that the therapy makes them better in any way," said committee member Deborah Grady, professor of epidemiology, biostatistics, and medicine, University of California, San Francisco. "If there is no proven benefit for them, they shouldn't be taking testosterone."   -- Christine Stencel


Testosterone and Aging: Clinical Research Directions. Committee on Assessing the Need for Clinical Trials of Testosterone Replacement Therapy, Board on Health Sciences Policy, Institute of Medicine (2004, 240 pp.; ISBN 0-309- 09063-6; available from the National Academies Press, tel. 1-800-624-6242; $37.95 plus $4.50 shipping for single copies).

The committee was chaired by Dan Blazer, professor of psychiatry and behavioral sciences, Duke University Medical Center, Durham, N.C. The study was funded by the National Institute on Aging and the National Cancer Institute.



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Copyright 2005 by the National Academy of Sciences