Testosterone Replacement Improves Aerobic Capacity

A new study finds that testosterone therapy may help older men who have experienced a decline in endurance improve aerobic capacity, and slow its decline with age.

If proven safe in the long-term, restoring testosterone to normal levels may boost a critical measure of physical performance and enhance quality of life for these patients, says Thomas W. Storer, PhD, director of the exercise physiology laboratory at Brigham and Women’s Hospital of Harvard Medical School, and lead study author.
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In an effort to investigate whether testosterone supplementation improves measures of aerobic function such as peak oxygen uptake and the gas exchange lactate threshold, Storer and colleagues analyzed data from subjects in a large randomized controlled study of men over age 65 who low testosterone levels and difficulty performing the usual physical activities associated with daily living. Over the course of 6 months, 28 men in 1 group received 10 milligrams of testosterone gel, while 36 men in a second group received a placebo gel. In addition, all subjects completed a cycle exercise test in order to measure their peak aerobic fitness before and after the 6-month study.

Men taking testosterone showed a slight improvement in aerobic fitness, while those taking the placebo gel demonstrated a slight decline. This small increase in aerobic capacity among the testosterone group eliminated the anticipated decrease that men typically experience with natural aging, according to the authors.

In addition, the men taking testosterone showed an age-related decline in the peak oxygen uptake that was 3.4 times less than expected. The rate of decline among the men taking a placebo accelerated to nearly twice the expected rate. Meanwhile, the decrease in gas exchange lactate threshold was significantly smaller in the testosterone group than in the placebo group, according to the researchers, who note that longer-term studies are needed to evaluate safety and durability of effect.

“Improving physical performance or delaying its decline are important therapeutic objectives” for primary care practitioners treating male patients with low testosterone, says Storer.

“Our data, derived from a relatively small subset of subjects from the TOM trial, revealed a small testosterone effect, suggesting a slight increase or maintenance of measures of aerobic performance. However, until larger studies are done, and the risks and benefits are analyzed carefully, we do not have any recommendations.”

The results were presented in a poster at ICE/ENDO 2014, the joint meeting of the International Society of Endocrinology and the Endocrine Society, held June 21 – June 24 in Chicago.

—Mark McGraw