It’s well known that testosterone levels decline after a certain age. That age is 30, and they decline by about one percent each year thereafter. To counteract this gloomy biological process, many men undergo testosterone therapy. A new study, however, finds that testosterone therapy might not be for everyone. It found that the treatment increased the risk of heart attack, strokes, and death in older men who had low testosterone — hypogonadism — and other health problems.

Study participants, who were all in their 60s, with health problems including high blood pressure, unhealthy, cholesterol, and diabetes. When compared to participants who didn’t take testosterone supplements over the course of three years, they were 30 percent more likely to die, or have a heart attack or stroke. What’s interesting about the study, however, is that participants who took testosterone were healthier and younger than those who didn’t at the beginning of the study, the researchers said.

“It does kind of raise the question of, maybe when patients and their physicians are thinking about starting testosterone therapy, potential risks such as the ones we looked at should be in that discussion,” Dr. P. Michael Ho, who worked on the study at the VA Eastern Colorado Health Care System in Denver, told Reuters.

Hypogonadism develops when the body doesn’t develop enough testosterone. It can cause a slew of physical and emotional changes in adult men, including erectile dysfunction, infertility, decreased muscle mass and hair growth, breast growth, loss of bone mass, fatigue, difficulty concentrating, and hot flashes. For these reasons and more, the number of annual prescriptions for testosterone therapy increased five-fold between 2000 and 2011, according to the researchers, AFP reports.

The study involved over 8,700 veterans in their early 60s. They all underwent heart imaging tests and many had risk factors associated with heart disease. Of these participants, 1,223 underwent testosterone therapy. After three years, the researchers found that 20 percent of those who didn’t take testosterone had either died, or had a heart attack or stroke — their average age was 64. The number of participants with a bad outcome jumped to 26 percent among the testosterone group — their average age was 61. Although there is no clear evidence why this may have occurred, the researchers speculated that the hormone might have caused blood platelets to clump together, accelerating the development of blood clots.

Dr. Ho also admitted that “these were sick, older veterans,” according to NBC News. “This is a modestly cautionary study about giving testosterone to men over 60 with multiple health problems,” Dr. Bradley Anawalt, an endocrinologist and professor of medicine at the University of Washington, told NBC. But at the very least, the study warrants a discussion between physician and patient.

In an accompanying editorial, Dr. Anne Cappola, from the Perelman School of Medicine at the University of Pennsylvania, questioned how these results could apply to the broader population of men. “For the men who are healthier, my question would be, why are you taking this? And is there any risk that’s acceptable for the benefits they’re getting?” Cappola told Reuters, adding that for healthy men, “we just don’t know what the benefits are.”

Source: Vigen R, Ho P, Rumsfeld J, et al. Association of Testosterone Therapy With Mortality, Myocardial Infarction, and Stroke in Men With Low Testosterone Levels. JAMA. 2013.