Efficacy of growth hormone-replacement therapy: Body composition and bone density

Adults with growth hormone deficiency (GHD), whether of childhood or adult onset, exhibit abnormalities in body composition and bone metabolism. It has been suggested that increased body fat may predispose adults with GHD to cardiovascular disease and that reduced bone density increases the risk of fracture. Studies of growth hormone (GH)-replacement therapy in these patients have demonstrated consistent effects on body composition with a decrease in body fat, both subcutaneous and visceral, and an increase in lean mass. Another consistent finding among GH-replacement studies is the significant effect on markers of bone turnover. Both bone resorption and bone formation are activated soon after initiation of GH therapy. The effects of GH replacement on bone mass are less clear, with variable results among, published studies. The varied duration of GH replacement between studies may explain the disparate results because bone remodeling is a long-term process. Long-term studies (greater than or equal to 18 months) demonstrate that GH replacement increases bone density, particularly at the spine and hip. Further studies are needed to address the long-term effect of GH replacement on cardiovascular mortality and fracture rates.