A new study published Tuesday suggests testosterone drugs for men with low levels of the hormone are not at an increased risk of developing atherosclerosis. However, other studies in the past have suggested an increased cardiovascular risk from using low-T drugs, and in 2015 the FDA finalized a decision that required companies to label their products with the possible risk for heart attack and stroke. So what's the deal?
"One of the hottest controversies in testosterone therapy is whether it's associated with cardiovascular risks, and whether there is a higher likelihood for strokes on testosterone," says Dr. Landon Trost, head of Male Infertility and Andrology at Mayo Clinic, who was not involved in the new study. "Testosterone therapy has a myth and promise of being the fountain of youth, and it's exploded since 2001. Everyone is trying to address [heart risks] right now."
The new study, published in the journal JAMA, found that among men with low levels of testosterone, there was no difference in the rate of build up in their artery walls, known as atherosclerosis, between those who used testosterone gel for three years and those who took a placebo. (Ironically, the study authors also found no improvement in overall sexual function, partner intimacy, and health-related quality of life in the men who took low-T drugs, either.)
Still, the case is far from closed. The new research didn't look at whether testosterone therapy is linked to more heart-related events like strokes, for instance. There is also the reality that many men taking low-T drugs do not, in fact, have clinically low levels of the hormone. What the drugs do in men with normal or high levels of the hormone is unknown.
The new paper also comes with plenty of caveats. It was funded by pharmaceutical companies that sell low-T treatments; one author works for a pharmaceutical company; another consults for Eli Lilly, which makes a low-T drug; and a third scientist has received research and personal fees from pharmaceutical companies, as well as having low-T-drug-related patents pending. (This was all in the mandatory "conflict of interest disclosures" section of study.)
As TIME reported in July 2014, some medical professionals have expressed concern over whether testosterone products are safe or if they even revitalize men like they promise to. Trost, for his part, says he gives patients the evidence and lets them make their own decisions, though he believes the research leans toward safety.
More research is needed.