Some study participants experienced 50 percent improvements in their ability to walk and in some cases, the muscle-strengthening effects lasted a year. Although 84 percent of the study subjects, with an average age of 67, were men, testosterone treatment with patches, gels or injections also produced improvements in women.
However, the pooled findings are from only 198 patients with chronic, stable heart failure, so they hardly provide the final word on treating the disorder with hormonal supplements, the study's lead author said. The observed improvements need to be reproduced in larger numbers of patients before testosterone can be recommended as therapy, said Dr. Justin Z. Ezekowitz, director of the Heart Function Clinic at the University of Alberta in Edmonton, Canada.
"We don't want patients and their loved ones rushing to buy testosterone supplements online, or physicians to misinterpret the findings," said Ezekowitz, who led the meta-analysis published today in the American Heart Association's journal Circulation Heart Failure.
The American Heart Association estimates that about 5.7 million Americans have congestive heart failure, about 2 percent of the population. The condition accounts for about a third of heart-related deaths.
When a person has heart failure, the heart cannot pump strongly enough to supply blood to the body, allowing fluids to build up in the lungs, arms and legs. It typically results from narrowed arteries (atherosclerosis), heart attack, heart valve diseases or infections that weaken the heart muscle.
Treatments include diuretics to eliminate fluid buildup, as well as several types of blood pressure drugs and others that also help reduce the heart's workload, and cardiac rehabilitation exercise programs. End-stage heart failure can be treated with heart transplants; occasionally, doctors implant a left ventricular assist device (LVAD), like the one that former Vice President Dick Cheney had before recently undergoing a transplant.
"These data are interesting," said Dr. Clyde W. Yancy, cardiology chief at Northwestern University in Chicago and a former American Heart Association president. Yancy's own research 20 years ago focused on exercise function in heart failure, a problem that he said remains pressing today.
Scientists have had several reasons to be curious about the use of testosterone in heart failure. Lower testosterone levels have been shown to be an independent risk factor for worse outcomes among men and women with heart failure. Low testosterone levels have been associated with decreased survival for men with coronary artery disease. And, testosterone supplementation has been associated with better cholesterol levels among men with heart disease, Ezekowitz and his colleagues noted in their study.
Despite interest in novel ways to improve exercise function in heart failure, "we should not yet view testosterone as the definitive answer," Yancy said, noting the lack of information about long-term cardiovascular effects of testosterone treatments. He called the small number of patients and limited follow-up in the four studies, in some cases just weeks to months, "insufficient to identify potential risks."
"As one assesses the magnitude of benefit observed, this is only a modest to moderate degree of improvement," Yancy said. "Finally, it is unfortunate but necessary to highlight that increased availability of testosterone as a therapeutic agent comes with significant abuse potential."
Abuse of testosterone, a steroid hormone that helps athletes and bodybuilders bulk up, has been associated with cardiovascular disease, increased risk of heart attack, and mood changes, as well as prostate cancer.