Association between P1NP and bone strength in postmenopausal women treated with teriparatide

Objective: To evaluate the association between P1NP and bone strength in postmenopausal women treated with teriparatide. Materials and Methods: This prospective study enrolled 248 postmenopausal women with severe osteoporosis treated with teriparatide. Procollagen type 1 N-terminal propeptide (P1NP) were assessed at baseline, 3, 6, and 12 months. Lumbar spine (LS), femoral neck (FN), and total hip (TH) bone mineral density (BMD) and LS trabecular bone score (TBS) were measured by Dual-energy x-ray absorptiometry at baseline and 12 months. Results: With teriparatide use, P1NP levels increase and peaked at 6 months. Significant increase in LS and hip BMD and LS TBS were also noted. The percentage change or absolute change >10 μg/L in PINP at 3 months was only related to changes in LS BMD at 12 months. With a median baseline P1NP level was 65.5 ng/mL, we found no correlation between P1NP and LS and hip BMD nor LS TBS. There was no association between LS TBS and axial BMD. After treatment, there was also no significance between the changes in TBS and axial BMD. Over the study period, 83.9% of the 248 participants were persistent with teriparatide at 3 months, 77.8% at 6 months, and 67.3% women at 12 months. Conclusion: P1NP levels may provide a signal of osteoporosis risk but is not related to bone strength. Early changes in P1NP may offer information regarding subsequent BMD response so standardized monitoring of P1NP levels at baseline and at 3 months should be considered during osteoporosis therapy. As an additional benefit, serum level monitoring during treatment may also improve medication persistence.