PROTEIN-METABOLISM IN GROWTH-HORMONE DEFICIENCY, AND EFFECTS OF GROWTH-HORMONE REPLACEMENT THERAPY

The effects of growth hormone (GH) treatment on protein metabolism wer e studied in adults with GH deficiency (GHD). A double-blind, placebo- controlled trial of recombinant human GH, 0.01 8 IU/kg/day for 1 month followed by 0.036 IU/kg/day for 1 month, was performed with isotopic whole-body protein turnover studies at 0 and 2 months. In all, 18 adul ts with GHD (9 men, 9 women; mean age, 46.6 years; range, 30-56 years) were studied. Whole-body isotopic leucine turnover using L-[1-C-13]le ucine was assessed by measuring leucine Ra (a measure of protein degra dation), non-oxidative leucine Rd (a measure of protein synthesis) and leucine oxidation rate. Lean body mass and circulating insulin-like g rowth factor I were significantly (p < 0.02) increased at 2 months in the GH-treated group, but not in the placebo group. There was no chang e in leucine Ra in either the placebo or GH-treated groups at 2 months . Leucine oxidation decreased (p < 0.0 1) and non-oxidative leucine Rd increased (p < 0.02) in the GH-treated group at 2 months. There was n o significant change in either leucine oxidation or non-oxidative leuc ine Rd in the placebo group at 2 months. These results indicate that t he increase in lean body mass resulting from GH treatment in adults wi th GHD is due to an increase in protein synthesis.