It was already known that low testosterone levels were associated with health problems, but this study suggests that high levels of the hormone are also a problem.
Researchers measured the testosterone levels of nearly 3 700 Australian men, aged 70 to 89, between 2001 and 2004. They then checked to see how many were still alive in December 2010. Those with the lowest testosterone levels had the highest death rate, followed by those with the highest levels.
Mid-range levels best
Men with mid-range levels of testosterone had the highest survival rate, according to the study, which was published in the Journal of Clinical Endocrinology & Metabolism.
"When the body metabolises testosterone, it produces dihydrotestosterone (DHT), which is tied to a lower risk of dying from ischemic heart disease," study author Bu Beng Yeap, of the University of Western Australia, said in a journal news release. In ischemic heart disease, there is reduced blood supply to the heart.
"Having the right amount of testosterone and higher levels of DHT might indicate that these men are in better health overall, or it could help them maintain good health as they grow older," he said.
Sex hormones important
Although the study found an association between high or low testosterone levels and increased death rates in men, it did not establish a cause-and-effect relationship.
"Sex hormones are an important predictor of mortality in older men, but we haven't determined if treatments to change testosterone and DHT levels can alter these outcomes," Yeap said.
He said additional research could help find ways to use this information to improve the health of older men.
The US National Library of Medicine has more about testosterone.