WASHINGTON, Aug. 10 (UPI) -- Researchers found that returning testosterone levels to normal in men who have low levels of it lowered their risk of heart attack, strokeor death from any cause, contradicting previous studies that questioned the efficacy of the hormone treatment.
The mixed results of previous studies have left doctors without concrete guidelines on treating men for low testosterone, with the Food and Drug Administration advising against over-prescription because of an increased risk of heart attack and stroke.
The new study is said to be significant because it considered more than 83,000 patients over the course of 15 years, from 1999 to 2014.
"It is the first study to demonstrate that significant benefit is observed only if the dose is adequate to normalize the total testosterone levels," Dr. Rajat Barua, a cardiologist at Kansas City Veterans Affairs Medical Center, said in a press release. "Patients who failed to achieve the therapeutic range after testosterone replacement therapy did not see a reduction in [heart attack] or stroke and had significantly less benefit on mortality."
Researchers analyzed records for 83,010 male veterans, splitting them three groups: Men whose treatment was to restore testosterone to normal levels; men who were treated but whose levels did not return to normal; and men who were not treated. The men were followed-up with an average of 4.6 to 6.2 years after treatment.
The difference in benefit from testosterone treatment between the group restored to normal levels and those only treated for low testosterone was small, although those who got some kind of treatment saw a small benefit over the men who were not treated, the researchers said.
Compared to men who were untreated, however, the men whose levels returned to normal were shown to have 56 percent less risk of dying during the follow-up period, were 24 percent less likely to have a heart attack, and 36 percent less likely to have a stroke.
Researchers wrote in the study that future studies will need to clarify the effects of testosterone on the cardiovascular system. "The mechanisms for these effects remain speculative," they wrote.
The study is published in European Heart Journal.