In older men, testosterone replacement may improve aerobics, endurance

By Lorraine L. Janeczko

NEW YORK (Reuters Health) - Some older men with limited mobility and low testosterone levels may improve their aerobic capacity and slow its decline by taking replacement testosterone, a new study suggests.

Testosterone therapy improved men's peak oxygen uptake (VO2peak) and lessened its age-related decline, study investigators reported here in a poster June 22 at ICE/ENDO 2014, the joint meeting of the International Congress of Endocrinology and the Endocrine Society in Chicago.

Testosterone replacement is known to increase skeletal muscle mass and strength but its effects on aerobic performance in older men have not been evaluated until now, the authors wrote in their abstract.

"Our data should be considered as preliminary evidence that treatment with replacement doses of testosterone in older men with mobility limitations slows the age-related decline in one measure of physical functioning," wrote lead author Dr. Thomas W. Storer of Brigham and Women's Hospital in Boston, in email to Reuters Health.

"This is an important study, one of the few studies to show an important clinical difference in the effects of testosterone on muscular function and endurance. These results suggest that some older men with low testosterone levels who are given testosterone might improve their endurance and aerobic capacity; and furthermore, that this might blunt the effects of aging on diminishing endurance," Dr. Brad Anawalt of the University of Washington Medical Center in Seattle, said by phone.

To study whether testosterone supplementation improves aerobic function - the peak oxygen uptake (VO2peak) and gas exchange lactate threshold (LTGE) -- the authors conducted a randomized controlled trial of 64 community-dwelling men over age 65 who had low testosterone and difficulty performing their normal daily physical activities, but were otherwise healthy.

Every day for six months, the 28 men in the treatment group received 10 mg of testosterone gel and the 36 men in the placebo group received 10 mg of a placebo gel.

At six months, all participants completed a cycle exercise test to assess their peak aerobic fitness. The men performed a symptom-limited cycle exercise using a 10- to 15-watt ramp protocol and their breath-by-breath oxygen uptake was measured to determine their VO2peak and LTGE.

The researchers calculated VO2peak from the participants' final 15 seconds of exercise and used the V-slope method to detect LTGE. They compared the changes in VO2peak within and between the groups using paired and unpaired t-tests, respectively; and they examined the change between groups for VO2peak compared with its expected change over treatment with an unpaired t-test.

The treatment group improved slightly from baseline in VO2peak and LTGE while the placebo group declined in those values (P=0.12).

The treatment group's age-related decline in peak oxygen uptake was 3.4 times less than expected, while the rate of decline in the placebo group grew to nearly twice the expected rate.

The treatment group had a significantly smaller decrease in LTGE compared with the placebo group (P=0.03).

"Testosterone treatment might blunt the effects of aging," wrote Dr. Anawalt, who was not involved in the study. "A man who is 75 years old with no recent history of stroke or heart attack, who is frail, having problems with walking a block (and) other activities of daily life, might benefit from having his testosterone levels increase enough to have an important effect on his muscular function."

Dr. Storer cautioned, "It would be premature to use our intervention for improving aerobic function at this time. As with any drug, the risk-to-benefit ratio must be carefully weighed. At this time, we do not know if the testosterone effect we reported can be sustained over time and whether the safety profile would allow testosterone treatment for the effect we reported. As with all preliminary data, our study should be replicated ideally with much larger samples."

The study received funding from the National Institutes on Aging, Boston Claude D. Pepper Older Americans Independence Center, and the Boston University Clinical and Translational Science Institute.

The researchers' abstract for the meeting is online here: http://bit.ly/1tJYuTZ.

(c) Copyright Thomson Reuters 2014. Click For Restrictions - http://about.reuters.com/fulllegal.asp