BACKGROUND: It is well known that growth hormone (GH) stimulates animal growth, but studies on metabolic effects of growth hormone have recently been increasing. The purpose of this study was to clarify the effects of growth hormone treatment on body composition and glucose metabolism in hypophysectomized growth hormone-deficient rats. METHODS: The 20-week-old rnale Sprague-Dawley rats were hypophysectomized and replaced with cortisol and thyroxine for 8 weeks, then administered with recombinant human growth hormone for 2 weeks. Group 1 consisted of intact controls (n 15), while group 2 consisted of hypophysectomized controls (n 12), and group three consisted of those with GH treatment (n 13). The body weights, body composition, blood glucose levels, plasma insulin-like growth factor-I (IGF-I) levels, euglycemic hyperinsulinemic clamp test, and glycogen synthase activities in gastrocnemius muscle were measured before and after growth hormone treatment. RESULTS: Plasma IGF-I levels in GH-treated group increased to intact control group levels after 2 weeks of GH treatment. There were significant changes in body composition after the treatment (fat mass significantly decreased and lean body mass significantly increased). There were no changes in glucose metabolism in peripheral tissue after 2 weeks of GH treatment. CONCLUSION: Human GH treatment (4 IU/kg/day) in adult hypophysectomized GH-deficient rats changed the body composition, but did not alter the glucose metabolism in peripheral tissue.