In older men with low testosterone levels, testosterone replacement therapy improves their risk factors for cardiovascular disease and diabetes, according to two new studies. The results will be presented at The Endocrine Society's 90th Annual Meeting in San Francisco.

Testosterone deficiency becomes more common with age, occurring in 18 percent of 70-year-olds, said a coauthor of both studies, Farid Saad, PhD, of Berlin-headquartered Bayer Schering Pharma. Low testosterone levels are linked to the metabolic syndrome-a cluster of metabolic risk factors that increase the chances of developing heart disease, stroke, and type 2 diabetes-and other health problems, including loss of bone and muscle mass, depression, and decreased libido.

Yet the risks and benefits of hormone replacement therapy are unclear in older men, he said.

Saad's research showed that restoring testosterone to normal levels in hypogonadal, or testosterone-deficient, men led to major and progressive improvements in features of the metabolic syndrome. Furthermore, men older than 63 benefited as much as younger men, they found. Treatment lasted a year and used a slow-release, injectable form of the hormone (testosterone undecanoate) that is not yet available in the United States.

All 95 men in the studies (ages 34 to 69 years) had the metabolic syndrome. To receive this diagnosis, patients must have three of the following five risk factors: increased waist circumference (abdominal fat), low HDL ("good") cholesterol, high triglycerides (fats in the blood), high blood pressure, and high blood sugar.

The first study showed that testosterone treatment significantly reduced waist circumference, total cholesterol, LDL ("bad") cholesterol, triglycerides, and body mass index (a measure of body fat). Treatment also increased "good" cholesterol. Improvements were progressive over 12 months, indicating that benefits may continue past a year, Saad said.

In the second study, the researchers divided the patient population into three groups by age: less than 57 years, 57 to 63 years, and more than 63 years. They found that the oldest men had similar improvements in metabolic risk factors to the youngest men.

Additionally, the investigators looked at the degree of testosterone deficiency before treatment. This beginning level of testosterone deficiency did not predict the beneficial outcome, they found. Men whose subnormal testosterone levels were not as low as the others had similar improvements in metabolic risk factors to men with the lowest levels, according to Saad.

"We conclude that if elderly men have a deficiency of testosterone, it is worthwhile to treat them with testosterone," he said.