Deficiency of the growth hormone-insulin-like growth factor-I axis potentially involved in age-related alterations in body composition

Because the body composition effects of growth hormone and insulin-like growth factor-I (IGF-I) are opposite to those of advancing age, it has been hypothesized that the decreased activity of the growth hormone-IGF-I axis is partly responsible for the loss of bone and muscle mass that characterizes normal human aging. The aim of the present cross-sectional analysis was to test this hypothesis in a well-defined community-based sample of 245 healthy elderly women, Dual-energy X-ray absorptiometry was used to measure body composition. To establish the major determinants of total bone mineral content (TBBMC), we assessed the relationships betwen TBBMC and age, height, weight, body mass index, muscle strength and serum concentrations of IGF-I, calcidiol, calcitriol, parathyroid hormone and sex hormone-binding globulin, Total body lean mass (TBLM), an indication of muscle mass, was related to the following potential determinants: age, habitual physical activity and serum IGF-I. Multiple regression was used to adjust for potential confounders. A significant relationship between circulating IGF-T and TBLM was not apparent in this study, On the other hand, serum IGF-I was found to be an independent predictor of TBBMC, despite the inclusion of established determinants of bone mass. These findings suggest that the demineralization of the skeleton in aging women is in part due to a deficiency of the somatotrophic axis.