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.