Researchers from the University of Texas Medical Branch reported on July 2 that they found no link between testosterone therapy and heart attack risk.
Their findings are directly opposite those from a study in January. Researchers from the University of California Los Angeles and other institutions said the therapy can double the risk of heart attack in men with existing heart disease.
The FDA, in a review published Sept. 3, said it could find no evidence of either risk or benefit in men prescribed testosterone therapy. It hasn’t been shown that symptoms such as a decrease in energy level and sexual function stem from an age-related decline in testosterone, the review said, and “the need to replace testosterone in these older men remains debatable.”
Because of their limitations, studies on the issue have not provided “convincing evidence” that testosterone therapy is associated with cardiovascular problems, the FDA said. But the agency also noted the increasing popularity of testosterone therapy. In 2010, 1.3 million patients received a prescription for testosterone; by 2013, this had risen to 2.3 million patients.
What have the major studies found about testosterone therapy and heart attack?
"We have many studies now showing different results that conflict," says Bradley Anawalt, MD, chief of medicine at the University of Washington Medical Center, Seattle. He is familiar with the research but was not involved in the two recent studies.
Some researchers have found a higher risk of heart attacks, while others haven't. In those that have found some risk, the degree varies. Some studies consider whether the men had pre-existing heart disease.
In the UCLA study, researchers looked at the medical records of nearly 56,000 men using testosterone therapy. Ninety days after starting the therapy, the risk of a heart attack doubled -- compared to a year before starting treatment -- for men 65 and above and for younger men with heart disease.
In the University of Texas study, researchers looked at more than 6,000 men ages 66 and older who were treated with testosterone. The researchers compared them to more than 19,000 men 66 and older who did not get testosterone.
They found no difference in the risk of heart attack in the two groups, says study leader Jacques Baillargeon, PhD, director of research in the division of epidemiology and outcomes at the University of Texas Medical Branch, Galveston. Baillargeon says he even found testosterone may offer some protection for men at the highest risk of heart attack. But he says that finding should be duplicated by other researchers to see if it holds up.