Early changes in biochemical markers of bone formation correlate with improvements in bone structure during teriparatide therapy

Context: Biochemical markers of bone turnover may reflect bone structure during anabolic treatment. Objective: The objective was to evaluate associations between changes in biochemical markers and structural and dynamic bone parameters during teriparatide treatment. Design: This study was a randomized, multicenter, double-blind, placebo-controlled fracture prevention trial, with 20-month median treatment duration for biopsy subset. Setting: The trial was conducted at 11 clinical study sites. Patients: Sixty-one postmenopausal women with osteoporosis who had paired transiliac biopsy specimens participated in the study. Interventions: Once-daily sc injections of either placebo or teriparatide (20 or 40 μg) were administered. Main outcome measures: The study measured: 1) serum and urinary biochemical markers of bone formation [bone alkaline phosphatase and procollagen I C-terminal propeptide (PICP)] and resorption (N-telopeptide and deoxypyridinoline); and 2) structural and dynamic analyses of bone biopsies, including two-dimensional (2D) histomorphometry and three-dimensional (3D) micro-computed tomography evaluations measured at baseline (n = 57) and 12 (n = 21) or 22 (n = 36) months. Results: U-N-telopeptide/creatinine and serum-PICP correlated with bone structure and dynamic indices at baseline, respectively. Changes in bone alkaline phosphatase at 1 month correlated with changes at 22 months in 2D wall thickness (r = 0.73; P = 0.001), trabecular bone volume (trabecular bone volume per total volume, BV/TV) (r = 0.58; P <0.05), marrow star volume (r = -0.51; P = 0.05); 3D trabecular thickness (r = 0.49; P <0.05), and BV/TV (r = 0.54; P <0.05). Changes in PICP at 1 month correlated with changes in wall thickness (r = 0.60; P = 0.01), and 2D BV/TV (r = 0.51; P <0.05) at 22 months. Changes in markers at 6 or 12 months were not associated with changes in structural or dynamic parameters. Conclusions: Early (1-month) changes in biochemical markers of bone formation, but not resorption, correlated with improvements in bone structure after 22 months of teriparatide therapy.