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Jan. 19, 2007 -- A growing number of middle-aged and elderly men are using testosterone creams, gels, and patches in an effort to feel young again, but there is little evidence the treatments are either effective or safe.
That is the conclusion of investigators from the Mayo Clinic who conducted two research analyses of testosterone therapy.
The studies they reviewed examined the risks from such treatment for heart disease and stroke and the benefits for boosting sexual function.
The researchers found that far too few quality studies have been published to accurately assess the treatment's safety and usefulness.
"Patients and their physicians should be able to make therapeutic decisions with a clear idea of what the risks and benefits are, but in this case that isn't possible," researcher Victor M. Montori, MD, MSc, tells WebMD. "There is still a lot of uncertainty about this treatment."
Roughly 2.4 million prescriptions for testosterone were filled in the U.S. in 2004 -- more than twice the number filled just four years earlier, according to pharmaceutical sales figures.
Such treatment has clear benefits for men with very low testosterone levels, often caused by surgical or chemical castration (using a drug to block production of testosterone in the body).
But the benefits of boosting testosterone levels in otherwise healthy agingmen experiencing natural declines in hormone levels are not as well understood.
Backers of the treatment say it can increase energy, libido, and general well-being; promote muscle growth; and protect against heart disease and bone loss.
On the flip side, there are suggestions that testosterone treatment may actually increase a man's risk of heart disease as well as prostate cancer and benign prostate growth.
Montori and colleagues in two different analyses reviewed studies examining the impact on sexual dysfunction and risk for heart diseaseand stroke.
Small to moderate improvements were seen in erectile function and libido, but the researchers concluded the sexual studies were inconsistent.
They also found the studies examining risk for heart disease and stroke to be lacking, saying large trials of men at risk for cardiovascular disease are needed.
"We have a situation where physicians and patients are essentially in the same boat," Montori says. "Neither is fully informed about testosterone therapy, because the long-term research just hasn't been done."
The researchers' reviews are published in the January issue of the journal Mayo Clinic Proceedings.
Better studies are urgently needed, Montori says, to avoid repeating what he calls "the estrogen disaster."
Millions of women took estrogen to protect against a wide range of diseases associated with aging, until a major study linked estrogen's use by older women to an increased risk of heart disease and breast cancer.
"I would contend that the quality of the evidence that we have about the safety and efficacy of testosterone therapy is much weaker than the evidence that we had when we were prescribing estrogen for just about everything," he says.
In a review of the research published late in 2003, an expert panel convened by the Institute of Medicine also found little evidence of the effectiveness and long-term safety of testosterone therapy in healthy, aging men.
That group called for large studies designed to examine the risks and benefits of testosterone therapy for such men.
Dan G. Blazer, MD, of Duke University, who lead the panel, tells WebMD we know little more about these risks and benefits today than we did three years ago.
"We don't have a clear picture of side effects, so we can't say that this drug is dangerous," he says.
"But, on the other hand, we don't have a lot of evidence that it is effective," says Blazer. "My concern is that its use as an antiaging drug will explode before we have the answers."