Millions of men, mostly over the age of 50, are now using testosterone therapy to treat a broad array of symptoms -- erectile dysfunction, weight gain, listlessness -- thought to be caused by low testosterone levels, which the pharmaceutical industry in copious advertising calls "Low-T."
But a major new study from a team of researchers at Brigham and Women's Hospital in Boston -- one of the biggest double-blinded studies of the therapy so far -- indicates that testosterone doesn't work as advertised.
The team, led by endocrinologist Dr. Shalender Bhasin, gave 306 men over the age of 60, all of whom had low to normal levels of testosterone, either testosterone gel or a placebo every day for three years. And patients who were given testosterone exhibited no more improvement in sexual function or quality of life than the control group.
The study's authors posit that "increasing testosterone levels above the lower limit of the normal range in healthy men does not further improve sexual function."
Bhasin explained that the benefits of testosterone therapy are clear for men who have "unequivocally low testosterone" because of testicular or pituitary issues.
"But what our study shows is that middle aged and older men whose testosterone levels are in the normal range -- or slightly below normal -- do not benefit to the same degree, and that they should not indiscriminately use testosterone," he said.
This finding strikes a blow to the multibillion dollar industry that has sprung up around testosterone in recent years. Pharmaceutical companies and for-profit clinics have reaped huge profits by convincing relatively healthy men that taking supplemental hormones will make them stronger, more attractive and more virile.
The study's news wasn't all bad for testosterone. Some earlier studies had suggested that testosterone therapy could put men at higher risk for cardiovascular problems such as heart attack and stroke. But the Brigham and Women's team found that testosterone therapy did not increase their subjects' risk for atherosclerosis, or hardening of the arteries, an important precursor to such cardiovascular events.
Another major study, published last week, even suggested that effective testosterone therapy could reduce men's risk for cardiovascular events. Unlike the Brigham and Women's study, this one was a not a double-blind, placeboed trial -- the gold standard -- but rather a retrospective analysis of the medical records of approximately 83,000 veterans. Yet it showed a striking reduction in cardiovascular problems among men who got testosterone therapy that increased their testosterone levels to the norm.
Yet even Dr. Rajat Barua, the author of the veteran study, admitted that the mechanics connecting testosterone levels and cardiovascular problems are too poorly understood -- and the evidence is too mixed -- to recommend testosterone therapy for cardiovascular issues alone, much less for men with normal testosterone levels.
In short, Bhasin said, "It's too early to put this stuff in the water supply."
This article has been updated with more specific information about which cardiovascular patients would be well served by testosterone therapy.