Testosterone replacement therapy (TRT) may improve self-reported physical function in older men with mobility limitations, but there are some caveats, according to researchers.

The Physical Function Trial (PFT) was 1 of 7 Testosterone Trials funded by the National Institute on Aging to assess the effect of TRT in older men with low testosterone (less than 9.5 nmol/L on average), difficulty in walking or climbing stairs, and walking speed of less than 1.2 meters per second. Participants in the trials were assigned to receive 1% testosterone gel (50 mg testosterone) or placebo gel daily for 12 months.

Previously reported results from the trials proved puzzling. TRT users displayed greater improvements in walking distance than placebo recipients in all trials—except the PFT. Treated men not enrolled in the PFT walked 8.9 meters farther on the 6-minute walk test than untreated men. In addition, TRT users scored higher than placebo recipients on the physical component of Short Form-36 (SF-36) in all trials—including the PFT. Treated men not enrolled in the PFT scored 4 points higher than placebo users.

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In the new analysis, Shalender Bhasin, MD, of Brigham and Women’s Hospital in Boston, and colleagues further investigated whether TRT effects differed according to baseline gait speed or other factors. According to results published in Lancet Diabetes and Endocrinology, testosterone-treated men with good gait speed (baseline walking speed of 1.2 meters per second or more) walked 14.2 meters longer on the 6-minute walk test and scored 4.9 points higher on the SF-36 physical component compared with placebo recipients. Likewise, compared with the placebo group, testosterone-treated men with mobility limitations walked 7.6 meters longer on the 6-minute walk test and scored 3.6 points higher on the SF-36 physical component.

With respect to perceived improvement, TRT recipients were 2 and 3 times more likely to report better walking performance on the patient’s global impression-of-change form than placebo recipients in the PFT and other testosterone trials, respectively. Dr Bhasin’s team found that the modest improvement in walking distance significantly correlated with increases in testosterone, free testosterone, dihydrotestosterone, and hemoglobin levels.

TRT did not reduce fall frequency. Twenty-seven percent of patients in both the TRT and placebo groups reported falling at least once during the intervention period.

“The treatment effect on mobility measures was small and seemed to be related to baseline gait speed and self-reported mobility limitation,” the authors wrote. “These effects might not, by themselves, justify use of testosterone therapy in older men with low testosterone concentrations. Thus, testosterone therapy should probably not be started specifically to improve physical function, although men who are treated with testosterone for other reasons could have some improvement in physical function.”

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Bhasin S, Ellenberg SS, Storer TW, et al. Effect of testosterone replacement on measures of mobility in older men with mobility limitation and low testosterone concentrations: secondary analyses of the Testosterone Trials. Lancet Diab Endocrinol. 2018 Nov;6(11):879-890. DOI:10.1016/S2213-8587(18)30171-2.