|A new study found that testosterone promotes|
prostate cancer in rats.
Testosterone use has soared in the last decade among older men seeking to boost energy and feel younger. One study published in The Journal of Clinical Endocrinology & Metabolism found that the number of American men who started testosterone therapy has nearly quadrupled since 2000, despite concerns about potential cardiovascular risks. The Endocrine Society's Clinical Practice Guidelines on testosterone therapy in adult men recommend prescribing testosterone only to men who have unequivocally low levels of the hormone and decreased libido, erectile dysfunction or other symptoms of hypogonadism, a condition that results from low testosterone.
Two dose-response studies examined the incidence of prostate cancer in rats. The rats were given testosterone through slow-release implant devices. Before the rats were dosed with testosterone, some of the animals were given injections of the carcinogenic chemical N-nitroso-N-methylurea (MNU). These rats were compared to a control group that received MNU but had empty slow-release devices implanted.
Among the rats that received testosterone without the carcinogenic chemical, 10 to 18 percent developed prostate carcinomas. Testosterone treatment alone did not induce specific tumors at other sites, but compared with control rats, it caused a significant increase in the number of rats with malignant tumors at any site. When rats were exposed to testosterone and the carcinogen, the treatment caused prostate cancer in 50 to 71 percent of the rats. Even when the hormone dose was too low to elevate testosterone levels in the bloodstream, half of the rats developed prostate tumors. Animals that were exposed to the carcinogenic chemical but not testosterone did not develop prostate cancer.