Testosterone Found to Increase the Risk of Prostate Cancer

Researcher urges caution in prescribing testosterone therapy in men who have not been diagnosed with hypogonadism.

Testosterone therapy may carry an increased risk for prostate cancer, according to the results of a recent study.

The study, published online October 7, 2014 in the journal Endocrinology, found that testosterone raised the risk of prostate tumors and worsened the effects of carcinogenic chemical exposure in rats. As a result, researchers are urging caution in prescribing testosterone therapy to men who have not been diagnosed with hypogonadism, the study noted.

"This research demonstrates that testosterone on its own is a weak carcinogen in male rats," said study's author Maarten C. Bosland, DVSc, PhD, in a press release. "When it is combined with cancer-causing chemicals, testosterone creates a hospitable environment for tumors to develop. If these same findings hold true in humans, there is serious cause for public health concern."

Adult men are recommended to use testosterone therapy when they exhibit unequivocally low levels of the hormone, in addition to decreased libido, erectile dysfunction, or other symptoms of conditions that result from low testosterone.

In evaluating a 2 dose-response in the incidence of prostate cancer, rats were given testosterone through slow-release implant devices. Additionally, prior to being dosed with testosterone, some of the rats were given injections of the carcinogenic chemical N-nitroso-N-methylurea (MNU).

The rats were then compared to a control group that also received MNU, but with implants of empty slow-release devices. In rats receiving testosterone without the carcinogenic chemical, 10 to 18% developed prostate carcinomas.

By itself, treatment was not found to induce specific tumors at other sites, but testosterone caused a significant increase in the number of control rats with malignant tumors at any site.

In rats exposed to testosterone and carcinogen, prostate cancer developed in 50 to 71% of the rats. Half of rats developed prostate cancer when the hormone dose was too low to increase testosterone levels in the bloodstream. Prostate cancer did not develop in rats who were exposed to the carcinogenic chemical alone.

"Since the growth of testosterone therapy is relatively recent and prostate cancer is a slow-moving disease, there are at present no data to determine if testosterone could heighten the risk of prostate cancer in humans," Bosland said. "While human studies are conducted, it would be prudent to limit testosterone prescriptions to men with symptomatic clinical hypogonadism and avoid testosterone use by men for non-medical purposes, including addressing normal signs of aging."