At some point in their 40s, men’s testosterone production begins to slow. By some estimates, levels of this hormone drop by about 1% a year. As men get into their 50s, 60s, and beyond, they may start to have signs and symptoms of low testosterone. These include reduced sex drive and sense of vitality, erectile dysfunction, decreased energy, lower muscle mass and bone density, and anemia. When severe, these signs and symptoms characterize a condition called hypogonadism
Researchers estimate that hypogonadism affects two to six million men in the United States. Yet it is an underdiagnosed problem, with only about 5% of those affected receiving treatment, according to the FDA. Deciding which patients should receive testosterone supplementation has proved tricky, however. For example, little consensus exists on what constitutes low testosterone. (The Endocrine Society considers a man to have low testosterone if the blood level is less than 300 ng/dl; some physicians set higher or lower benchmarks.) In addition, some men may have low blood levels of testosterone but not experience any symptoms. And few large, randomized studies on the long-term risks or benefits of testosterone supplementation have been completed.
ne of the most heated debates centers on whether testosterone fuels prostate cancer. If that’s true, say some experts, then why do men develop prostate cancer when they are older, at the same time their testosterone levels are dropping? (See Figure 1.) Others point to the fact that many men with prostate cancer, especially those with advanced or metastatic cancers, take hormone therapy that nearly stops the production of testosterone to tamp down the disease. Under the influence of hormone therapy, tumors regress