Insulin-like Growth Factor-I and Bone Mineral Density

To assess the relationship between insulin-like growth factor-I (IGF-I) and bone mineral density (BMD) 201 healthy postmenopausal women (age 41–68 years) within 10 years of menopause were studied. In all subjects, BMD at the lumbar spine and left hip were measured using dual-energy X-ray absorptiometry and blood samples were obtained. In all subjects, serum IGF-I and parathyroid hormone (PTH) were measured. In a subgroup of these subjects serum concentrations of IGF-binding protein-3 (IGFBP-3), osteocalcin (OC), bone-specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase (TRAP), and carboxyterminal propeptide of type I procollagen (PICP) were also measured. Serum IGF-I correlated significantly with age (r = −0.159, p = 0.0241), serum OC (r = 0.226, p = 0.0131), BALP (r = 0.259, p< 0.0001), and TRAP (r = 0.261, p< 0.0015), but not with PICP, PTH, or BMD at any site. Although there was a strong correlation between IGF-I and IGFBP-3 (r = 0.559, p< 0.0001), there was no correlation between IGFBP-3 and any of the markers of bone turnover (OC, BALP, TRAP, or PICP) nor with PTH or BMD at any site. We conclude that IGF-I and markers of bone turnover are related, but there is no relationship between IGF-I and BMD.