GH and IGF-I as therapeutic agents for osteoporosis

Current strategies for the treatment of osteoporosis rely almost exclusively on agents whose pharmacological actions are primarily antiresorptive. There is, therefore, growing interest in developing agents able to stimulate bone formation, such as GH and IGF-I, which play an important role in bone metabolism, being essential for the development and growth of the skeleton and for the maintenance of bone mass. Furthermore, the decline in GH/IGF-I axis with aging, is correlated with the increased risk of osteoporosis and fragility fractures in elderly population. Several studies investigated the potential of GH and/or IGF-I as therapeutic agents in osteoporotic patients (post-menopausal women and idiopathic osteoporotic men), showing a clear correlation between the used GH dosage (and the obtained IGF-I plasmatic levels) and the increase in bone turnover markers and/or bone mineral density (BMD) at different skeletal sites. In particular, the use of IGF-I/IGFBP-3 complex seems to be very useful and safe in older women with recent hip fracture. Also the possibility of combining GH/IGF-I treatment with antiresorptive drugs (such as calcitonin and alendronate) has been explored, showing controversial results on BMD at different skeletal sites. In summary, based on the current evidence, it is clear that circulating GH and IGF-I are critical for skeletal modeling, bone acquisition and age related bone loss. Nevertheless, controlled studies with fracture incidence as endpoints are needed to fully assess the potential of these bone anabolic agents in the treatment of osteoporosis.