NEW YORK - Older men who take testosterone are more likely to have a heart attack or stroke or die over the next few years, new research indicates.
The study included men who were in their early 60s, on average. Most of them already had blocked heart arteries, high blood pressure, diabetes and other health problems.
So it's unclear what the findings mean for younger, healthier men who take testosterone, 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," said Dr. P. Michael Ho.
He worked on the study at the VA Eastern Colorado Health Care System in Denver.
Testosterone is recommended for men who make too little of the hormone on their own, a condition called hypogonadism. For them, testosterone can boost strength and sexual functioning.
But advertising campaigns for testosterone products may be reaching a bigger pool of men - who are tired or depressed, for instance, but don't have clinically low testosterone levels.
One study found the proportion of middle-aged US men getting testosterone treatment more than tripled over the last decade. Not all of those men had undergone a blood test to see if they really needed it.
The long-term risks of taking testosterone are largely unknown, according to Ho and his colleagues. Some studies suggest it may worsen sleep apnea or prostate cancer.
The researchers collected information on about 8,700 men seen at Veterans Affairs hospitals who had low testosterone levels. Each of those men underwent a test to check for plaque buildup in his heart arteries between 2005 and 2011.
Sometime after that test - which the researchers used to assess initial heart health - one in seven of the men started using testosterone gels, patches or injections.
In the three years following their heart tests, 20 per cent of men who didn't start taking testosterone had a heart attack or stroke or died. That compared to almost 26 per cent of those who had started using testosterone.
When the researchers took into account the extent of men's initial artery blockages, they calculated that using testosterone was tied to a 29-per cent higher risk of heart attack, stroke or death.
Those differences weren't due to variations in blood pressure or cholesterol or in the use of heart drugs between the testosterone and non-testosterone groups.
In fact, men who started using testosterone initially had fewer health problems than those who didn't, the researchers wrote Tuesday in the Journal of the American Medical Association.
The finding that they still ended up having more cardiovascular problems "says, maybe there really is something that's happening with that group," Dr. Anne R. Cappola told Reuters Health.
Cappola, from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, wrote an editorial published with the new study.
She agreed it's hard to know how the results apply to younger men without pre-existing heart problems. But in that case, especially when men don't have low testosterone, it's even more important to consider possible risks, she said.
"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 are getting?" Cappola said. Among healthy men, "We just don't know what the benefits are."
"I think (taking testosterone) is an individual decision, but I think it's worth weighing the potential benefits of testosterone therapy versus any potential risks before starting it," Ho told Reuters Health.
What's more, Cappola added, "If a man is taking testosterone and he doesn't feel any better, he should stop it."