Low serum concentrations of insulin‐like growth factor I are associated with femoral bone loss in a population‐based sample of postmenopausal women

OBJECTIVE: Cross-sectional studies suggest that the decline in insulin-like growth factor-I (IGF-1) levels with age may contribute to age-associated bone loss. However, prospective data on the relation between circulating IGF-I and bone loss in old age have not yet been reported. DESIGN: A longitudinal study (follow-up time 3.3 years) of the change of bone mineral density (BMD) at the lumbar spine and femoral neck in relation to serum IGF-I. PATIENTS: A population-based sample of 173 elderly men and 107 postmenopausal women without medical conditions or medication known to significantly affect BMD or serum IGF-I levels. MEASUREMENTS: BMD at the lumbar spine and femoral neck at baseline and after a mean follow-up-time of 3.3 years, serum-IGF-I, insulin-like growth factor binding protein 3 (IGFBP-3), sex hormone-binding globulin (SHBG) and biologically available testosterone (BAT). RESULTS: In women, there was a graded negative relationship between quartiles of serum IGF-I and bone loss at the proximal femur (P = 0.04), which persisted after adjustment for potential covariables of bone loss and serum IGF-I. In subgroup analysis the association between serum IGF-I and change in BMD was only apparent in women more than 10 years past menopause (r = + 0,38, P = 0.01). No association between serum IGF-I levels and changes in BMD was observed in men. IGF-I levels were not associated with changes in spinal BMD. CONCLUSIONS: Our data suggest that low circulating levels of IGF-I in elderly women are associated with greater femoral bone loss, and support previous findings of gender differences in the relation between serum IGF-I and BMD in older age.