OBJECTIVE: The objective of this study was to evaluate the relationship between serum insulin-like growth factor binding protein profiles and bone mineral density measurements and biochemical markers of bone turnover in postmenopausal women. STUDY DESIGN: Sera from 37 normal healthy postmenopausal women and 14 postmenopausal women with osteoporosis were analyzed for insulin-like growth factor binding proteins and osteocalcin by Western ligand blotting and radioimmunoassay, respectively. Bone mineral density measurements were performed by dual-energy x-ray absorptiometry. Urinary calcium and creatinine excretion were also determined. The data were analyzed statistically by analysis of variance and the least-squares method. RESULTS: The serum insulin-like growth factor binding protein-2 ratio (Insulin-like growth factor binding protein-2 intensity/total insulin-like growth factor binding protein intensity) in postmenopausal women with osteoporosis was significantly higher (p < 0.02) than that in normal healthy postmenopausal women, but the serum insulin-like growth factor binding protein-3 ratio in women with osteoporosis was significantly lower (p < 0.01). The serum insulin-like growth factor binding protein-2 ratio correlated negatively with the bone mineral density of the lumbar spine (p < 0.0001), femoral neck (p < 0.05), trochanter (p < 0.01), and Ward's triangle (p < 0.05), but there was a significant positive correlation between the serum insulin-like growth factor binding protein-3 ratio and the bone mineral density of the lumbar spine (p < 0.001) and trochanter (p < 0.05). No correlations between serum insulin-like growth factor binding protein levels or serum ratios and biochemical markers of bone turnover were noted. CONCLUSION: The measurement of serum insulin-like growth factor binding protein profiles might be useful in identifying postmenopausal women at risk for osteoporosis. (AM J OBSTET GYNECOL 1996;174:1511-7.)