Background:Testosterone treatment in obese dieting men augments the diet-associated loss of fat mass, but protects against loss of lean mass. We assessed whether body composition changes are maintained following withdrawal of testosterone treatment
Methods:We conducted a pre-specified double-blind randomised placebo-controlled observational follow-up study of a randomized controlled trial (RCT).Participants were men with baseline obesity (body mass index >30kg/m2) and a repeated total testosterone level <12nmol/L,previously enrolled in a 56-week testosterone-treatment trial combined with a weight loss program.Main outcome measures weremean adjusted differences (MAD) (95% confidence interval), in body composition between testosterone and placebo-treated men at the end ofthe observation period.
Results:Of the 100 randomised men, 82 completed the RCT, and 64 the subsequent observational study. Median[IQR] observation time after completion of the RCT was 82 weeks [74; 90]in men previously receiving testosterone (cases) and 81 weeks [67; 91]in men previously receiving placebo (controls), p=0.51. At end of the observation period, circulating total testosterone levels were no different between cases and controls, MAD -0.4nmol/L (-2.5, 1.7) p=0.71. Similarly, there were no between group differences in fat mass,MAD
-0.8kg, (-3.6, 2.0), p=1.0, in lean mass, MAD-1.3kg (-3.0, 0.5), p=0.39, and in appendicular lean mass, MAD-0.1kg/m2 (-0.3, 0.1), p=0.45. During observation, cases lost more lean mass, MAD-3.7kg (-5.5, -1.9), p=0.0005 and appendicular lean mass, MAD-0.5kg/m2 (-0.8, -0.3), p<0.0001 compared to controls.
Conclusions:The favourable effects of testosterone therapy on body composition in men subjected to a concomitant weight loss program were not maintained at 82 weeks after treatment cessation.