Structural and Mechanical Responses to Intermittent Parathyroid Hormone Treatment, Discontinuation and Cyclic Administration Regimens

Bone mineral density rapidly decreases upon withdrawal from intermittent parathyroid hormone (PTH) treatment despite its potent effect of promoting bone formation. To better understand this adverse phenomenon, this study first aimed to investigate the phenotype of PTH withdrawal in both intact and estrogen-deficient rat model by using a well-designed experiment combined with innovative longitudinal imaging techniques and localized cellular activities. Due to observing a continuous anabolic window upon early discontinuation of PTH treatment in estrogen-deficient animals, we propose a potential effective treatment strategy, the short cycles of PTH and antiresorptive treatment regimen, which could extend the anabolic windows by increasing the number of newly activated modeling-based bone formation (MBF) sites. Lastly, to understand the structure-function relationships of bone tissue formed through MBF compared to the remodeling-based bone formation (RBF), we developed an innovative imaging platform with a mechanical testing platform to determine the mechanical properties of MBF and RBF and their long-term contributions in intact animals