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 bo ne 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 bon e 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 postmenopausa l women without medical conditions or medication known to significantly aff ect 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 facto r binding protein 3 (IGFBP-3), sex hormone-binding globulin (SHBG) and biol ogically available testosterone (BAT). RESULTS In women, there was a graded negative relationship between quartile s of serum IGF-I and bone loss at the proximal femur (P = 0.04), which pers isted 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 = + 0,3 8, 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 spina l BMD. CONCLUSIONS Our data suggest that low circulating levels of IGF-I in elderl y 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.