Testosterone Replacement Therapy Boosts Aerobic Capacity

The joint meeting of the International Society of Endocrinology and the Endocrine Society was the site of a presentation on June 22 concerning findings discovered from a clinical trial of sedentary men with low testosterone levels and mobility problems which revealed increased aerobic capacity among those treated with testosterone.

The current study evaluated data from 64 men, mean age 73, with low testosterone enrolled in the Testosterone in Older Men with Mobility Limitation Trial.

Participants in the trial were treated with 10 milligrams of testosterone in gel form or a placebo gel daily for six months.

Cycle exercise tests conducted at the beginning and end of the treatment period provided measures of aerobic function, including peak oxygen uptake and gas exchange lactate threshold.

The gas exchange lactate threshold is an excellent functional measure of the ability to do work over a prolonged period.

The rate remained steady during the 6-month study in the testosterone-treated men but declined significantly (and to a greater-than-expected extent based on average measures) in the placebo-treated controls

When the trial ended, men who received a placebo saw a drop in peak oxygen uptake, while those treated with testosterone saw an increase in their peak oxygen uptake.

Not only was the age-related decrease in peak oxygen uptake during exercise, or peak VO2 was 3.4-fold less in the testosterone-treated men than would be expected, the rate of decline in peak VO2 in placebo-treated controls was near twice the expected rate for the age-matched general population.

Researchers concluded that this accelerated decline was probably due to their limited mobility and low testosterone levels.

"We believe 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," announced lead author Thomas W. Storer, Ph.D., who is the Director of the Exercise Physiology Laboratory at Brigham and Women's Hospital in Boston.

"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 is something we think is going to be clinically meaningful."

"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," he added.

"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."

"We think the mechanisms involved in this benefit are many," Dr. Storer continued.

“Among them are testosterone’s demonstrated ability to increase muscle mass and thereby generate more force during exercise; increased RBC formation; stimulation of tissue capillarity to allow more blood flow to the exercising muscle; and stimulation of mitochondrial biogenesis, which increases oxygen uptake by muscle tissue.”

However, he added that although these results are quite promising, he doesn’t think this work is ready for prime time application in daily clinical practice.

He plans to further evaluate the safety of this treatment and the durability of the effects in a study with larger patient numbers and more prolonged treatment.

The study received funds from the National Institute on Aging, the Claude D. Pepper Older Americans Independence Center, and Boston University.

Dr. Storer reported having no relevant financial conflicts.

Reference

Testosterone replacement enhances aerobic capacity in mobility-limited men

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