Serum levels of insulin-like growth factor (IGF) I, IGF-binding protein (IGFBP)-2, and IGFBP-3 in osteoporotic patients with and without spinal fractures

The present study was performed to investigate the role of insulin-like growth factor I (IGF-I), IGF-binding protein-2 (IGFBP-2), and IGFBP-3 in age-dependent bone loss in postmenopausal Japanese women, One hundred and sixty-five Japanese women aged 43-88 years (mean age, 62) were enrolled in the cross-sectional study, Bone mineral density (BMD) was measured at the lumbar spine, femoral neck, and midradius by dual-energy X-ray absorptiometry or single-photon absorptiometry, Serum levels of IGF-I, IGFBP-2, and IGFBP-3 were measured by radioimmunoassay, BMD at all sites as well as serum levels of IGF-I and IGFBP-3 declined with age, while the serum IGFBP-2 level increased with age, Serum IGFBP-3 and -2 levels were positively and negatively correlated with the serum IGF-I level, respectively, Serum IGF-I and IGFBP-3 levels showed positive correlationship with BMD at any site, particularly at the midradius, while the serum IGFBP-2 level showed negative correlation with BMD, Multiple regression analyses showed age-independent positive correlation between the serum IGF-I level and BMD at all sites as well as age-independent positive correlation between the serum IGFBP-3 level and midradius BMD. The relationship between susceptibility to osteoporotic spinal fracture and serum IGF-I, IGFBP-3, or -2 levels was examined by decade to exclude the influence of aging, Serum levels of IGF-I and IGFBP-3 were significantly lower in subjects with spinal fractures than those without fractures at any decade, No significant difference of serum IGFBP-3 level was observed between subjects with and without fractures, The present findings suggest that IGF-I and IGFBP-3 are important to maintaining bone mass quantitatively as well as qualitatively, and that the determination of serum IGF-I and IGFBP-3 levels could be clinically useful to predict the severity of osteoporosis, particularly the risk of bone fracture associated with osteoporosis.