PTH and postmenopausal osteoporosis: PTH stimulates osteoblast differentiation and proliferation26 and indirectly activates osteoclasts by regulating RANKL and OPG in osteoblast cell lines.27 Differing from the efficacy of PTH observed in the treatment of postmenopausal osteoporosis, clinical studies involving the use of PTH after fracture have shown mixed results, ranging from positive effects to no effects on fracture healing.28–30 These findings suggest that fracture-induced changes in the internal environment may affect the effect of PTH on bone metabolism.