DXA-based hip structure analysis (HSA), conducted as a subgroup of the Fracture Prevention Trial (DXA-HSA study) [9], also showed that periosteal apposition appeared to be reduced in patients receiving daily teriparatide in comparison with a placebo-treated group. On the other hand, some studies reported daily treatment with teriparatide

seemed to stimulate new bone formation on the Selleck S3I-201 periosteal and endosteal surfaces [14, 15]. Thus, periosteal and endosteal apposition may be stimulated within a certain time window or may vary depending on skeletal sites, such as weight bearing or non-weight bearing bone [13]. Bone generally expands in diameter with age [16, 17], as less bone density requires a wider bone to maintain bending strength. selleck compound It has been speculated that expansion is a homeostatic adaptation to a net bone loss in order to maintain bone strength [18, 19]. This age-related adaptive response was not seen in the placebo group of the current study. Once-weekly injection of teriparatide increased cortical thickness with no change in cortical perimeter at the femoral neck. Thus, it is tempting to speculate that as a result of increased cortical thickness (which improves bone strength), periosteal apposition may not be

required under once-weekly teriparatide treatment. Actually, a change in BR based upon improvement in cortical thickness was observed in the teriparatide group. The r 2 between percent change of cortical thickness and that of BR

in the teriparatide group ROS1 was higher than the placebo group. As illustrated in Fig. 4, teriparatide improved all geometry and biomechanical parameters, while maintaining their relationships with changes in cortical thickness (as in the placebo group). However, the distribution patterns of their relationships indicate that the effect of teriparatide is in the exact opposite direction of age-related skeletal changes. It is suggested, therefore, that compared with the changes in the placebo group, once-weekly teriparatide injection reverses age-related deteriorations in bone structure and strength by increasing cortical thickness/CSA and total vBMD, not increasing cortical perimeter, and improving biomechanical parameters. In our previous study which characterized femoral neck geometry in patients with hip versus trochanteric fractures and compared them with age-matched controls [7], patients with femoral neck fracture had a significantly longer hip axis length (HAL), lower cross-sectional moment of inertia (CSMI), and higher BR, while those with trochanteric fractures had a smaller cortical CSA of the femoral neck. Once-weekly teriparatide may improve all these geometric changes.