Value of measuring muscle performance to assess changes in lean mass with testosterone and growth hormone supplementation

We hypothesized that treatment with testosterone (T) and recombinant human growth hormone (rhGH) would increase lean mass (LM) and muscle strength proportionally and an in a linear manner over 16 weeks. This was a multicenter, randomized, controlled, double-masked investigation of T and rhGH supplementation in older (71 ± 4 years) community-dwelling men. Participants received transdermal T at either 5 or 10 g/day as well as rhGH at 0, 3.0 or 5.0 μg/kg/day for 16 weeks. Body composition was determined by dual-energy X-ray absorptiometry (DEXA) and muscle performance by composite one-repetition maximum (1-RM) strength and strength per unit of lean mass (muscle quality, MQ) for five major muscle groups (upper and lower body) at baseline, week 8 and 17. The average change in total LM at study week 8 compared with baseline was 1.50 ± 1.54 kg (P < 0.0001) in the T only group and 2.64 ± 1.7 (P < 0.0001) in the T + rhGH group and at week 17 was 1.46 ± 1.48 kg (P < 0.0001) in the T only group and 2.14 ± 1.96 kg (P < 0.0001) in the T + rhGH group. 1-RM strength improved modestly in both groups combined (12.0 ± 23.9%, P < 0.0001) at week 8 but at week 17 these changes were twofold greater (24.7 ± 31.0%, P < 0.0001). MQ did not significantly change from baseline to week 8 but increased for the entire cohort, T only, and T + rhGH groups by week 17 (P < 0.001). Despite sizeable increases in LM measurements at week 8, tests of muscle performance did not show substantive improvements at this time point.