Growth hormone (GH) treatment in GH-deficient adults: effects on muscle size, strength and neural activation

The effects of 6 months of recombinant growth hormone (GH) treatment (0.5 IU kg-1 per week) on muscle size, strength and neural activation (EMG) was studied in eight adults with childhood onset GH deficiency (GHD). Before treatment, height, body mass (BM) and lean body mass (LBM) of the GHD subjects were significantly lower (P < 0.01) from those recorded in eight healthy controls, while no significant differences were found between the body mass index (BMI) of the two populations. Thigh muscle + bone cross-sectional area (CSAM+B) and lower limb muscle plus bone volume (LLVM+B) of the GHD patients were 66.1 +/- 13.7% and 47.6 +/- 6.8% of those recorded in the controls (P < 0.01), whereas no difference in CSA/height2 was found between the two groups. By contrast, LLVM+B/height3 was 82.0 +/- 19.0% that of the controls (P < 0.05). Similarly, quadriceps muscle strength (MVC) of the GHD patients was 63.2 +/- 12.4% that of controls (P < 0.01), while no significant differences in the force per unit area (F/CSA) and per body mass (F/BM) were found. After 6 months of GH treatment LBM increased by 6.0 +/- 4.2% (P < 0.02), CSAM+B by 14.5 +/- 12.7% (P < 0.01) and LLVM+B by 10.1 +/- 7.3% (P < 0.01), absolute differences from the normals still persisting. However, the LLVM+B/height3 of the GHD patients after treatment was no longer significantly different from that of the controls. Quadriceps MVC increased by 9.8 +/- 12.0% (P < 0.02), differences from the controls being still significant, whereas the F/CSA and F/BM did not change. A right shift of the integrated EMG/Force relation, with no change in the maximal integrated EMG (iEMG) activity, was observed in the patients after treatment. In conclusion, the current study shows that adults with childhood onset GHD have a reduced skeletal muscle mass and strength which seem to be positively influenced by 6 months of GH treatment.