Testosterone therapies meant to treat low sex drive and moodiness could be linked with an increased risk of heart attack.

Researchers noticed a two-fold increase in instances of heart attack shortly after the start of hormone therapy in men under 65 with a history of heart disease, a University of California-Los Angeles news release reported. The same was found to be true in men over 65.

This is the largest study that has looked at heart disease in men using testosterone supplements.

Three smaller studies had warned of cardiovascular risks associated with testosterone therapy; the research inspired the team to perform a larger study on the subject.

"We decided to investigate cardiovascular risks of this therapy in a large health care database since these previous studies were modest in size and only focused on men 65 and older," the study's senior author, Sander Greenland, a professor of epidemiology at the UCLA Fielding School of Public Health and a professor of statistics in the UCLA College of Letters and Science, said in the news release. "Our study allowed us to examine cardiovascular risk in men under the age of 65 and to replicate the findings in men over 65."

The team looked at the health care records of 55,593 men who had been prescribed testosterone therapies.  There were 48,539 participants under the age of 65 and 7,054 were older.

"Their research led to the finding of a twofold increase in men under 65 with heart disease and confirmed the earlier findings of a twofold increase in men over 65 with or without heart disease," the news release reported.

"The extensive and rapidly increasing use of testosterone treatment and the evidence of risk of heart attack underscore the urgency of further large studies of the risks and the benefits of this treatment," Greenland said. "Patients and their physicians should discuss the risk of heart attacks when considering testosterone therapy."