TUESDAY, June 17 (HealthDay News) -- Low testosterone levels put men at high risk for cardiovascular disease, diabetes and early death, but testosterone replacement therapy may help better the odds, according to new studies.

Some experts believe that low testosterone levels, which become more common with age, are linked to several health conditions. These include loss of bone and muscle mass, depression, decreased libido, and, most important, the metabolic syndrome -- a cluster risk factors that increase the chances of developing heart disease, stroke and type 2 diabetes.

The studies, all of which were expected to be presented at The Endocrine Society's annual meeting, in San Francisco, suggest that therapy to raise testosterone back to normal levels may have several positive effects.

One study showed that testosterone treatment significantly reduced abdominal fat, total cholesterol, LDL ("bad") cholesterol, triglycerides and body mass index (a measure of body fat). It also helped raise HDL ("good") cholesterol.

Researchers in a second study found that men older than 63 benefited as much as younger men.

"We conclude that if elderly men have a deficiency of testosterone, it is worthwhile to treat them with testosterone," co-author of both studies, Farid Saad of Berlin-headquartered Bayer Schering Pharma -- a drug company that makes a form of testosterone therapy -- said in a prepared interview.

A third study added to previous evidence that low testosterone increases one's chance of early death from any cause in the long run.

In the study, funded in part by drug maker Novo Nordisc, researchers looked the causes of death in almost 2,000 German men aged 20 to 79 years. The men with low testosterone at the start of study, which had an average follow up period of 7 years, had a more than 2.5 times greater risk of dying during the next 10 years compared with men with higher testosterone. These men tended to be older, fatter and had a greater prevalence of diabetes and high blood pressure than the men with higher testosterone levels, Haring said.

This difference was not explained by age, smoking, alcohol intake, level of physical activity or increased waist circumference (a risk factor for diabetes and heart disease), according to researcher author Robin Haring, a Ph.D. student from Ernst-Moritz-Arndt University of Greifswald, Institute for Community Medicine.

Low testosterone levels predicted increased risk of death from cardiovascular disease and cancer but not death of any other single cause, the study found.

More information

The Hormone Foundation has more about low testosterone.