Lack of Effect of Calcitonin on the Regulation of Vitamin D Metabolism in the Rat1

The infusion of calcitonin into intact rats increases the accumulation of 1,25-dihydroxy-[26-27-3H]vitamin D3 from 25-hydroxy-[26,27,-3H]vitamin D3 in blood, but has no effect on thyroparathyroidectomized rats using a variety of protocols. Furthermore, the vitamin D status of the animals did not alter the results. Inasmuch as no effect of calcitonin could be found on the accumulation of other vitamin D metabolites as well as 1,25-dihydroxyvitamin D3, it is concluded that calcitonin apparently plays no direct role in the regulation of vitamin D metabolism and that the previous report of an effect of calcitonin on vitamin D metabolism in vivo is probably the result of a secondary response of the parathyroid gland.