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 Obese men who receive testosterone therapy increase their muscle mass and lose more total body fat than men who receive only advice about a healthy diet and exercise, according to a new study that will be presented Sunday at The Endocrine Society’s 92nd Annual Meeting in San Diego.

The randomized controlled clinical trial, considered the gold standard of medical studies, also proved the capacity for testosterone to lower cholesterol levels in obese men ages 40 to 70, said one of the study’s authors, Rob McLachlan, MD, PhD.

“High-quality data on the effects of testosterone therapy on obese men have been lacking,” said McLachlan, professor and head of clinical andrology at Prince Henry’s Institute in Clayton, Victoria, Australia. “This study has rigorously tested the effects on a range of health indicators.”

Specifically, the investigators assessed body composition (muscle and fat content), insulin sensitivity (the ability to successfully clear glucose, or sugar, from the bloodstream into the body’s cells), cholesterol and triglycerides (fats in the blood), and blood glucose.

Forty obese men with testosterone levels in the low to low-normal range participated in the study, and all received ongoing advice regarding healthy lifestyle choices to lose weight. They were randomly assigned to either the testosterone treatment group or the control group, which consisted of no intervention besides the diet and exercise advice. Men in the treatment group received six injections during the one-year study of a long-acting, injectable form of testosterone undecenoate (Nebido, 1,000 milligrams). The drug is not yet available in the United States.

Of the 35 men who completed the study, 19 were in the testosterone group and 16 were in the control group. Although total weight did not change in either group, the testosterone-treated men had significant changes in body composition not seen in the controls, the authors reported. Their total body fat decreased by an average of 10 percent, and their skeletal muscle increased by about 6 percent.

Additionally, in the testosterone group, the LDL (“bad”) cholesterol and total cholesterol levels fell by about 10 percent each. Cholesterol levels did not change in the control group.

“These initial favorable results require confirmation in larger studies of longer duration,” McLachlan said.

Bayer Schering Pharma, Berlin, supplied the drug and gave partial funding for this study. The Australian National Health and Medical Research Council awarded McLachlan a fellowship.

 

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Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Md. To learn more about the Society, and the field of endocrinology, visit our web site at www.endo-society.org.