Men with signs of heart problems who take injections of testosterone or use gel containing the hormone may have an increased risk of heart attack or stroke, a new study finds. The findings call for more cautious prescribing of testosterone, doctors say.
In 2011, 5.3 million prescriptions for testosterone were written in the United States. Testosterone therapy is often prescribed to men in order to counteract the age-related decline in the hormone and improve sex drive, bone density and muscle mass. But the benefits and risks of the long-term use of testosterone therapy are not well known.
In the new study, Dr. Rebecca Vigen, a researcher at the University of Texas, and her colleagues looked at 9,000 male veterans who had undergone coronary angiography between 2005 and 2011, a procedure for testing the arteries when people have symptoms such as chest pain or are at high risk for heart problems. The men, whose average age was 60, were also found to have low testosterone levels during their exam, and 1,200 of them started testosterone therapy after their tests.
The researchers followed up with the men after an average of 2.4 years after their angiography. During the study, 26 percent of men who were receiving testosterone therapy had either a heart attack or a stroke, or died from any cause, while 20 percent of men who did not receive testosterone therapy had experienced such events or died. [5 Myths About the Male Body]
In other words, the men who used testosterone therapy had a 30 percent increased risk of heart attack, stroke or dying, compared with men who didn't use the hormone, and the results held after being adjusted for several other factors that could have affected the outcomes, according to the study, published today (Nov. 5) in the Journal of the American Medical Association (JAMA).
The results "make us take a pause, and make sure that everyone taking testosterone is taking it for the right reasons and is experiencing benefits," said Dr. Anne Cappola, an associate professor of medicine at the University of Pennsylvania who wasn't involved in the study.
Doctors and patients should be wary of the aggressive marketing used by testosterone manufacturers, Cappola said.
"There's a lot of marketing out there of testosterone and low-T syndrome, and a lot of men who want to feel better," she said. "So that marketing appeals to them, but they are not hearing any of the risks side, which is often harder to quantify."
In the United States, rates of testosterone prescription tripled between 2000 and 2011, reaching sales of $1.6 billion in 2011, according to a previous study.
The researchers said the new study was prompted by a recent clinical trial of testosterone therapy in men who were at high risk for heart disease. That study was stopped early, due to higher rates of heart problems in the group receiving the hormone.
All of the men in the new study generally had higher rates of medical conditions — including coronary artery disease, diabetes and previous heart attacks — than men in the general population.
Cappola said the study participants represented a "real-world" population of men who have more health problems than the men enrolled in most randomized clinical trials do.
The researchers noted that they couldn't verify whether the men in the study had been prescribed testosterone according to doctors' guidelines, which require doctors to draw blood in the morning on two different days and look for medical problems that could be related to testosterone deficiency. Cappola said there's evidence that sometimes patients are prescribed testosterone without having their hormone levels properly checked.
It is still unclear whether the results extend to other populations of men — for example, men of the same age group who are taking testosterone for low-T syndrome or for anti-aging purposes, or younger men taking it for physical enhancement.
"Although physicians should continue to discuss the benefits of testosterone therapy with patients, it is also important to inform patients that long-term risks are unknown and there is a possibility that testosterone therapy might be harmful," the researchers said.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.