Calcitonin, parathyroidectomy and modelling of bones in the growing rat.

After calcitonin injection, parathyroidectomy, or both, in young growing rats, broadening of the proximal femoral metaphysis with lack of normal concavity of the medial and lateral contours was observed radiographically. Histologically, this abnormal modelling was associated with retarded osteocytic osteolysis. Further manifestations of decelerated resorption included retention and extension of the chondroid core in the secondary spongiosa, retention of cartilage in the cortex and a large increase in the number of cementing lines.