SKELETAL EFFECTS OF GROWTH-HORMONE AND IGF-I IN ADULTS

Three processes occur in the skeleton; modelling during growth, fractu re repair and remodelling, Remodelling is bone resorption coupled to b one formation, and alterations in the remodelling balance are the fina l pathway to bone loss. Therapeutic agents are now available to minimi ze the normal phenomenon of age-related bone loss and protect against osteoporotic fracture. These agents reduce the rate of bone resorption , have positive effects on bone mass and some reduce fracture rates. N one, however, restore bone mineral to normal levels. GH has been consi dered for this role due to its positive effects in vitro and in vivo. GH-deficient adults have low BMD compared to healthy controls, and the reasons for this finding are discussed, A neglected factor is a measu rement artefact from the use of DXA. Long-term GH therapy can lead to clinically important increases in BMD in GH-deficient adults, The resu lts from studies of GH administration to healthy elderly populations a re also presented. The small rise of lumbar BMD or maintenance of BMD at the hip seen in these studies are no better than results achieved w ith cheaper, easier to administer therapies. Investigation of other ag ents in the somatotrophic axis, are, however, potentially promising an d warrant further investigation.