By Megan Rauscher

NEW YORK (Reuters Health) - Men with type 2 diabetes or the metabolic syndrome, or both, are prone to have low testosterone levels. If so, testosterone replacement therapy with a gel applied to the skin may improve their response to insulin and their sexual function, according to the results of a new clinical trial.

Testosterone levels fall if testicular function is subnormal, a condition termed hypogonadism. "Consideration should be given to screening type 2 diabetic and metabolic syndrome patients for hypogonadism," Dr. T. Hugh Jones told the Endocrine Society's annual meeting in San Francisco this week.

Jones, of Barnsley Hospital and the University of Sheffield in the UK, and colleagues tested the effect of a testosterone gel (Tostran) on insulin resistance and symptoms of hypogonadism in 221 men with low testosterone levels.

One average, the men were 60 years age with a body mass index of 32, in the obese range. Eighty percent had metabolic syndrome, 64 percent had type 2 diabetes, and 44 percent had both. They were randomly allocated to use the testosterone gel daily or a matching placebo gel.

The study showed a statistically significant improvement in insulin sensitivity in testosterone-treated men at 6 and 12 months, Jones reported.

Testosterone therapy also led to a significant improvement in the score on a standard assessment of erectile function after 6 and 12 months.

Adverse events were similar in the two groups. Skin-related problems were the most commonly reported adverse events, experienced by 19 (17 percent) placebo-treated and 27 (25 percent) testosterone-treated men.

"These data tell us that replacement therapy for low testosterone in hypogonadal males not only improves sexual function but, more importantly, can also have an impact on insulin sensitivity," Jones said. "Long-term improvements in insulin resistance may help to improve cardiovascular and other diabetes complications and improve quality of life in this at-risk population."

"Awareness of the problems caused by low testosterone is becoming more widespread and its connection to health issues like diabetes continues to become increasingly apparent," he added. "As the incidence of hypogonadism continues to grow along with the aging population, we need to ... implement a more rigorous screening program, particularly in men with type 2 diabetes."

The study was sponsored by ProStrakan, with US headquarters in Bedminster, New Jersey, makers of Tostran (also marketed as Fortigel, Tostrex and Itnogen).