Muscle function following testosterone replacement in men on opioid therapy for chronic non-cancer pain: A randomized controlled trial.

Abstract

Chronic pain and opioid treatment are associated with increased risk of male hypogonadism and subsequently decreased muscle function. A diagnosis of hypogonadism is based on the presence of low total testosterone and associated symptoms. The effect of testosterone replacement therapy on muscle function in men with chronic pain and low total testosterone remains to be investigated. To investigate the effects of testosterone replacement therapy on muscle function and gait performance in men treated with opioids for chronic non-cancer pain. A double-blind, placebo-controlled study. Forty-one men (>18 years) with opioid-treated chronic pain and serum total testosterone <12nmol/L were randomized to 24weeks testosterone replacement therapy (testosterone undecanoate injection three times/6 months, n =20) or placebo injections (n =21). Muscle function was measured as leg press maximal voluntary contraction, leg extension power using the Nottingham power rig and handgrip strength using a handheld dynameter. Gait performance was measured at usual and maximal gait speed on a 10-m track. Body composition (lean body mass and fat mass) was determined by dual-energy X-ray absorptiometry. Mann-Whitney tests were performed on ∆-values (24-0weeks) between testosterone replacement therapy and placebo. At baseline, median (interquartile range) age was 55 ± 13 years and BMI was 30.7 ± 5.2kg/m2 . ∆-muscle function and ∆-gait performance were similar between testosterone replacement therapy and placebo. Median ∆-leg press maximal voluntary contraction was 174.2 ± 406.7 Newton, following testosterone replacement therapy, and 7.6 ± 419.1 Newton, after placebo, p=0.091. ∆-lean body mass was significantly higher following testosterone replacement therapy compared to placebo, 3.6 ± 2.7versus 0.1 ± 3.5kg, respectively (p<0.001). Testosterone replacement therapy, compared to placebo, did not improve muscle function or gait performance despite increased lean body mass. Changes in body composition did not infer any changes in muscle function. 24weeks testosterone replacement therapy in opioid-treated men with pain-related male hypogonadism did not improve muscle function.