Tomographic (pQCT) and biomechanical effects of hPTH(1–38) on chronically immobilized or overloaded rat femurs

Six-month old rats chronically submitted to right hindlimb immobilization (IM) with mechanical overload (OL) of the left leg were treated 1 month later with 200 ug/kg/d of hPTH(1–38) for 15 or 75 days. Peripheral quantitative computed tomography (pQCT) scans and bending tests showed that hPTH increased cortical mass and volumetric BMD (vCtBMD) in both legs. However, elastic modulus of cortical bone and diaphyseal load-bearing capacity were improved only in OL bones. Improvement of diaphyseal strength was attributable to that of cortical bone quality, yet a stronger mechanostatic response of cortical modeling to bone material quality was also observed in treated OL bones. Data support hPTH(1–38) use for improving cortical bone mass and strength and point out a physical activity interaction with therapeutic results.