NEW YORK - In the ongoing saga of testosterone and male aging, a new report concludes that low levels of the sex hormone might raise men's risk of dying from heart disease.
Researchers followed more than 3,600 elderly men living on their own for about five years on average. Over that time, about six per cent died due to heart disease, with men who had low levels of so-called free testosterone leading the pack.
The results add to a confusing tangle of data. Some show low testosterone levels - sometimes called low T - are linked to earlier deaths, including those due to heart disease, while other data don't.
Pharmaceutical companies are also promoting testosterone therapy for problems like grumpiness, lack of energy and decreased libido, whose connection with the hormone is still unclear.
The main problem in this area - the question of causation versus correlation - is one that also mars the new report, according to Dr. Frederick Wu, who wasn't part of the study.
"Low T is associated with poor health," Wu, a hormone expert at the University of Manchester in the UK, told Reuters Health by email. "But it does not mean that low T is the cause of poor health or increased mortality."
Earlier this year, a large analysis of previous medical studies concluded that drooping testosterone is unlikely to curb a man's lifespan, but instead might just dip along with declining health.
Zoe Hyde of the Western Australia Center for Health and Aging, who worked on the latest study, said that was not a likely explanation when it comes to heart disease.
"There is good evidence that testosterone has beneficial effects with regard to the cardiovascular system. For example, testosterone has been shown to increase lean mass (including muscle), whilst decreasing fat mass. It can also have some positive effects on cholesterol levels," she told Reuters Health in an email.
The researchers, whose findings are published in the Journal of Clinical Endocrinology & Metabolism, did take into account other factors that might be relevant, such as age and high blood pressure.
But that still doesn't prove low testosterone is harmful to the heart, according to Wu.
"This conclusion is somewhat premature," he said.
What's more, one recent clinical trial that tested a testosterone gel on elderly men had to be stopped early because the drug turned out to cause heart problems - not prevent them.
In that trial, published in the New England Journal of Medicine last year, 23 men on hormone therapy developed complications like heart attack and stroke, compared to just five men who got inactive placebo treatment.
Hyde acknowledged that her study is not definitive.
"We need to wait for the results of clinical trials before we can properly understand both the benefits and also the risks of testosterone therapy," she said.