Decreased PTH Levels Accompanied by Low Bone Formation Are Associated with Vertebral Fractures in Postmenopausal Women with Type 2 Diabetes

OBJECTIVE: Patients with type 2 diabetes (T2DM) have an increased risk of vertebral fractures (VF) compared with non-T2DM controls due to poor bone quality. The aim of this study was to investigate the association between VF and bone turnover. RESEARCH DESIGN AND METHODS: We compared clinical parameters, such as serum PTH and osteocalcin (OC), between hospital-based Japanese T2DM patients (123 postmenopausal women and 132 men over 50 yr old) and medical checkup-based non-T2DM controls (189 women and 51 men). The association between PTH and OC levels was investigated, and the VF risks were compared for four subgroups classified by PTH and OC values. RESULTS: T2DM patients had lower PTH and OC levels than the controls for both sexes (P < 0.01). Multivariate regression analysis showed that PTH levels of T2DM patients were significantly and positively correlated with OC levels (women, r = 0.324, P < 0.01; men, r = 0.343, P < 0.01). When participants were divided into two subgroups based on mean PTH and OC levels, the group of T2DM women with lower PTH and lower OC levels had a significantly higher risk of VF than those with higher PTH and higher OC levels after adjusting for age, body mass index, hemoglobin A(1c), creatinine, 25-hydroxyvitamin D, and lumbar bone mineral density (odds ratio, 4.73; 95% confidence interval, 1.20-18.6; P = 0.026). CONCLUSIONS: Patients with T2DM had decreased PTH levels. In T2DM postmenopausal women, lower PTH levels accompanied by low bone formation may elevate VF risk independently of bone mineral density compared with higher bone formation, possibly as a result of reduced bone quality.