“Low T” ads promise men a vibrant, new lease on life with prescription testosterone gels and patches. And dozens of over-the-counter supplements claim to boost or “support” testosterone levels. Testosterone is a hormone that helps build muscle, reduce fat, strengthen bones, and boost sex drive. In men, it also helps produce sperm. Low testosterone levels may also decrease insulin sensitivity, so could testosterone supplements reverse that and prevent diabetes?
“Since testosterone increases muscle and reduces fat mass, it should improve insulin sensitivity,” notes University of Washington’s Stephanie Page, a testosterone expert.
In several small studies, men with type 2 diabetes and low testosterone levels who took the hormone improved their insulin sensitivity more than similar men who took a placebo.
“It will be important to see if these benefits are observed in larger studies of men with obesity or type 2 diabetes,” says Page.
But she cautions that the jury is still out on the safety of testosterone supplementation.
A 2010 trial that gave testosterone or a placebo to 209 men with low or low-normal levels (100 to 350 nanograms per deciliter of blood) was halted early because the men getting the hormone were five times more likely to have a heart attack, congestive heart failure, or some other cardiac trouble than the men taking the placebo.
Some other studies detected no increased risk, while still others saw a hint of one.
“The bottom line is that we don’t know what the risks of testosterone supplementation are because we don’t have the large randomized controlled trials we need to evaluate them,” says Page.
Source: Diabetes Care 34: 828, 2011; New Engl. J. Med. 363: 109, 2010; JAMA 299: 39, 2008; J. Clin. Endocrinol. Metab. 98: 1891, 2013.