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Could testosterone replacement therapy increase risk of prostate cancer?

Studies have been mixed so far, but recent animal research suggests it might. Previous studies have linked testosterone replacement to an increase in heart attack and stroke, prompting an increase in testosterone replacement lawsuits around the country.

Study Links Testosterone Therapy with Prostate Cancer

For the study, researchers used slow-release implant devices to give some rats (but not others) testosterone. Next, they injected some of the rats (but not others) with a chemical known to cause cancer (called “MNU”). They then compared the groups.

Results showed the following:

• Of the rats that received testosterone but not the carcinogenic chemical, 10 to 18 percent developed prostate cancer.
• Of the rats that were exposed to testosterone and the carcinogenic chemical, 51 to 71 percent developed prostate cancer.
• Even when the dosage of testosterone was too low to elevate testosterone levels in the bloodstream, 50 percent of the rats developed prostate cancer.
• Rats that were exposed to the carcinogenic chemical, but not to testosterone, did not develop prostate cancer.

The researchers recommended human studies to further examine the potential link between testosterone therapy and prostate cancer. They also advised healthcare providers to limit testosterone prescriptions in men who did not have hypogonadism, including men who were interested in the therapy for anti-aging reasons.

“These findings have potential significant public health implications for the use of testosterone therapy in men,” they wrote.

Other Studies Find Conflicting Results

These results seem to conflict with those from a recent human study, published in the Journal of Urology. For that study, researchers examined three ongoing studies of over 1,000 men—all diagnosed with hypogonadism (low levels of testosterone caused by a medical condition).

They found that long-term testosterone therapy does not increase prostate cancer in these men. It’s important to note, however, that these studies did not include men who had not been diagnosed with hypogonadism, leaving out a large population of men who are currently taking the drug.

Indeed, a 2013 study published in JAMA Internal Medicine found that a quarter of the men who were taking testosterone replacement drugs were not even tested for low testosterone.

Men Using Testosterone for the Wrong Reasons

The FDA approved the use of testosterone therapy strictly in men who had been diagnosed with hypogonadism, but in recent years, men have started asking about the therapy to treat typical signs of aging, including fatigue and muscle loss. Plaintiffs who have filed testosterone lawsuits claim this increased use is in response to manufacturer advertisements that presented the drugs as solutions for these types of symptoms.

In January 2014, the FDA announced that it was investigating the risk of stroke, heart attack, and death in men taking testosterone products. The convened a panel of experts in September 2014 to review the safety of such products as AndroGel and Testim. That panel recommended drug makers conduct additional tests to further evaluate the risks.

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