Some older men taking testosterone therapy may have a higher risk of heart attacks, stroke and death, say researchers raising questions about safe use of the hormone.
While prescriptions for testosterone have increased in the U.S. in the past decade, the Endocrine Society's Choose Wisely campaign recommends it should only be prescribed when there is biochemical evidence of testosterone deficiency.
Studies suggest that testosterone therapy, available as injections, patches or gels, improves sexual function, strength and bone mineral density.
In Tuesday's issue of the Journal of the American Medical Association, researchers in the U.S. compared 1,223 men taking testosterone with 7,489 men not using testosterone. They were in their early 60s on average, and had coronary angiography to check for blockages between 2005 and 2011.
At three years, the rate of deaths, heart attacks and strokes were 25.7 per cent in those who received testosterone therapy compared with 19.9 per cent in the no testosterone therapy, Dr. Rebecca Vigen of Southwestern Medical Center in Dallas and her co-authors found.
"These findings raise concerns about the potential safety of testosterone," the researchers concluded.
Use of testosterone therapy was associated with adverse outcomes among men with and without coronary artery disease.
It's unclear how the hormone might increase heart risks but it's possible testosterone might make blood substances called platelets stick together, which could lead to blood clots, the study authors said.
It's also not known whether the risks of harm apply to other men taking testosterone for "low T syndrome," for anti-aging purposes or younger men taking it for physical enhancement.
"In light of the high volume of prescriptions and aggressive marketing by testosterone manufacturers, prescribers and patients should be wary," Dr. Anne Cappola, an associate professor of medicine in the endocrinology division at the University of Pennsylvania said in a journal editorial accompanying the study.
A ongoing randomized trial of 800 men aged 65 or older with diminished walking ability, interest in sex, energy or memory receiving testosterone gel or placebo for a year could provide more information, Cappola said.
A 2007 study published in Canadian Family Physician found recommendations for clinical monitoring of men taking androgen therapy were not being followed in Manitoba at the time.
Dr. Nathaniel Polnaszek, a urologist with Scott & White Healthcare in Round Rock, Texas, said he prescribes testosterone for many men, mostly in their 40s and 50s, with low levels and erectile dysfunction or other symptoms. He called the study "concerning."
"This is something I'm going to be discussing with my patients," he said.
AbbVie, Inc., makers of the testosterone supplement, AndroGel, issued a statement in response to the study, saying it is approved by the U.S. Food and Drug Administration, and the risks are listed.
Possible side-effects shown on the package insert include high blood pressure, blood clots in the legs, and body swelling that may occur with or without heart failure.
The study was funded by the U.S. Department of Veterans Affairs.