Last Updated: 2008-01-01 16:00:32 -0400 (Reuters Health)

NEW YORK (Reuters Health) – Although use of testosterone supplements may increase lean body mass and reduce fat mass in older men, it does not improve functional mobility or cognition, according to a report in the Journal of the American Medical Association for January 2.

The study involved 237 healthy men between 60 and 80 years of age who were randomized to receive testosterone undecenoate 80 mg or placebo capsules twice daily for 6 months. All of the men had low normal testosterone levels (<13.7 nmol/L). A total of 207 subjects completed the study.

A variety of standard measures were used to assess functional mobility, cognitive function, bone mineral density, body composition, metabolic risk factors, quality of life, and prostate health.

Although lean body mass rose and fat mass fell in the testosterone group relative to the placebo group, this did not translate into improved functional mobility or muscle strength, lead author Dr. Marielle H. Emmelot-Vonk, from University Medical Center Utrecht in the Netherlands, and colleagues note. Likewise, no significant changes in cognitive function or bone mineral density were noted with testosterone use.

Testosterone had mixed metabolic effects. Use of the hormone enhanced insulin sensitivity, but was also associated with a drop in HDL cholesterol. Moreover, by the end of the study, 47.8% of testosterone-treated men had metabolic syndrome compared with 35.5% of those given placebo (p = 0.07).

Testosterone use also had little effect on quality of life, the report indicates.

In terms of safety, there was no evidence that testosterone use increased the risk of prostate cancer, the authors state.

"This study is, as far as we know, the largest study of testosterone supplementation with the most endpoints and a randomized, double-blind design," Dr. Emmelot-Vonk and colleagues state. "The findings in this study do not support a net benefit on several indicators of health and functional and cognitive performance with 6 months of modest testosterone supplementation in healthy men with circulating testosterone levels in the lower range."

JAMA 2008;299:39-52.

Copyright Reuters 2008. Click for Restrictions