Testosterone: The Fountain of Youth?
Many Questions Remain About Its Usefulness and Safety
It is not known how many older men are on testosterone replacement, but the numbers are believed to have increased dramatically since the FDA approved an easy-to-apply testosterone gel in the spring of 2000. News reports noted that sales of the gel quadrupled the following year.
The usefulness of the treatment for men with abnormally low testosterone levels is unquestioned. But it is less clear whether testosterone therapy offers benefits to aging men with naturally declining levels of the male sex hormone, says National Institute on Aging deputy director Stanley Slater, MD.
"We know that in most men, testosterone levels drop by about a third by the time they reach 65, but this is not the case for all men," Slater tells WebMD. "The question is, does it matter in terms of health whether a man has 30% less testosterone? And nobody knows the answer to that."
Slater says a good trial to determine if testosterone therapy increases the risk of prostate cancer would need a minimum of 6,000 men and would cost in excess of $100 million. A similarly large study would be needed to determine if testosterone replacement promotes or protects against heart disease.
In his editorial, Vastag writes that a Baylor College of Medicine researcher has proposed just such a study. But any plans to move forward are on hold -- pending conclusions from the Institute of Medicine special panel. In light of this delay, the study would not even begin until mid to late next year, with results expected at the end of the decade.
"Small studies have suggested that testosterone replacement therapy increases bone density and promotes lean body mass and less fat," Slater says. "These things are indicative of youth and health, but they are not the same thing. The real measures of health are whether there is sickness and loss of functionality. For these measures, we don't yet know if testosterone is helpful."