[The influence of parathyroid hormone on the process of fracture healing]

The influence of parathyroid hormone (PTH) on the process of fracture healing was examined using the fractured rats which were parathyroidectomized or given synthetic PTH. The biochemical and histological changes were studied. The results were as follows: I) Parathyroidectomized rats (PTX rats) showed decreased serum Ca, increased serum P and decreased serum PTH as observed in hypoparathyroidism. The fracture healing was impaired due to delay of both chondroclasis at the phase of endochondral ossification and secondary remodeling of primary cancellous bone. II) In rats treated with PTH (PTH rats) both serum Ca and P levels were increased at the early stage. Bone resorption as well as formation was also promoted at the early stage. At the late stage only bone formation remained good with poor bone resorption, indicating that secondary bone remodeling is decreased. The union of callus was impaired. Fracture healing was consequently delayed in both PTX and PTH rats. It is therefore suggested that PTH may be one of the important factors in fracture healing.