Increase in plasma calcitonin following femoral fracture in rats.

The secretion of calcitonin (CT) has been studied in male rats following a standardized, left femoral fracture after administration of subcutaneous fluanisone and fentanyl citrate anaesthesia. Twenty-five minutes after the fracture, the plasma concentrations of CT were increased by about 20 per cent in young and by about 60 per cent in adult rats compared to prefracture levels of the hormone. Three weeks later, plasma CT had decreased and was not significantly different from prefracture levels. Anaesthesia combined with femoral fracture did not influence plasma calcium significantly, whereas the plasma concentrations of calcium increased in young control rats during 35 minutes of anaesthesia alone. Plasma CT, however, remained unchanged in these control rats in the same period. In rats with a transplanted, CT-secreting, medullary thyroid carcinoma, femoral fracture did not alter the already high plasma concentrations of CT. It is suggested that increase in CT secretion is part of a general response to trauma.