Testosterone Therapy in Mobility-limited Older Men May Up Endurance

Testosterone replacement improves aerobic function in older men who have limited mobility and low testosterone levels, according to a new study.

“Testosterone replacement unequivocally increases skeletal muscle mass and strength. This is the first report of enhanced endurance performance as a result of testosterone therapy in men who have difficulty performing some physical tasks, but are otherwise healthy,” said lead author Thomas W. Storer, PhD, Director of the Exercise Physiology Laboratory at Brigham and Women’s Hospital of Harvard Medical School in Boston, Massachusetts.

"These findings are potentially relevant to older men who have experienced the age-related decline in endurance capacity that may be due in part to low testosterone. If proven safe over the long-term, restoring testosterone to normal levels may improve an important measure of physical performance and enhance their quality of life.”

Previously, the researchers have found that testosterone stimulates mitochondrial biogenesis, increases red cell mass, and tissue capillarity, “all of which would be expected to increase tissue oxygen delivery and aerobic performance. However, the effects of testosterone on aerobic performance in older men have not been evaluated,” said Dr Storer, who noted that aerobic fitness declines as people age.

To investigate whether testosterone supplementation improves measures of aerobic function― the peak oxygen uptake and the gas exchange lactate threshold―Dr Storer and his colleagues analyzed data from subjects in a large randomized controlled study of men over age 65 who had low total or free testosterone levels and difficulty performing the usual physical activities of daily living. For 6 months, 28 men in one group received 10 mg of daily testosterone gel and 36 men in a second group received a placebo gel. All subjects completed a cycle exercise test to measure their peak aerobic fitness before and after the 6-month study.

The men taking testosterone displayed a slight improvement in aerobic fitness while those taking placebo showed a slight decline. This small increase in aerobic capacity in the testosterone group eliminated the expected decrease that men generally experience with natural aging.

Among the men taking testosterone, the age-related decline in the peak oxygen uptake was 3.4 times less than expected, while the rate of decline among the men taking placebo accelerated to nearly twice the expected rate. The decrease in gas exchange lactate threshold was significantly smaller in the testosterone group than in the placebo group.

In conclusion, the researchers stated that “Testosterone therapy in mobility-limited older men was associated with improved VO2peak and attenuated its age-related decline.” They added that long-term intervention studies are needed to determine the durability of this effect and whether testosterone affects fatigue.

“At least in the short term, testosterone therapy may lessen the rate of decline of an important marker of physical fitness in older men with low testosterone. This may lead to reduced fatigue and improved quality of life," Dr Storer said.

The researchers presented their results on June 22, 2014 at ICE/ENDO 2014, the joint meeting of the International Society of Endocrinology and the Endocrine Society in Chicago.