A quantitative study of the effects of prolonged calcitonin treatment on alveolar bone remodelling in the golden hamster.

This study was carried out on adult golden hamsters, to correlate the effects of porcine calcitonin on serum Ca and P concentrations with changes in osteoclastic resorption of bone. After 1 month of treatment with 5 MRC units/kg/day, there was little effect on these parameters. On the other hand, the hormone appears to have an effect on the remodelling sequence, as indicated by a large and very significant decrease in the extent of resorption lacunae unoccupied by osteoclasts. It is suggested that the duration of the reversal phase, separating the end of active resorption from the beginning of active bone formation in each remodelling focus, is greatly decreased. This shortening is associated with a prolongation of the bone formation phase, and the extent of osteoid tissue is markedly and proportionally increased in the treated animals. After a prolonged administration, calcitonin does not seem to impede the formation of new osteoclasts, their number being only slightly diminished, but it remains possible that it does continue to inactivate these cells. The effect on the bone remodelling sequence could be either due to direct action on the osteoblasts or their percursor cells, or an indirect action via the osteoclasts.