Studies on Calcium Metabolism and Aging (II)

Calcitonin and aging

Abstract

Calcium metabolism has been known to change remarkably with advancing age. Although the mechanisms involved in the altered calcium metabolism with advancing age are not clearly understood, it is possible that these changes may involve an altered target organ response to calcitonin and/or parathyroid hormone or changes in the secretion rate of these hormones. In this study the role of calcitonin in the calcium metabolism with advancing age has been examined by comparing in rats of three different ages, 1) the recovery from CaCl₂ induced hypercalcemia, 2) the hypocalcemic response to thyroid cautery, 3) the hypocalcemic response to exogenous calcitonin and 4) the content of calcitonin in the thyroid gland. It was found that older rats exhibited a retarded recovery from hypercalcemia, a smaller response to exogenous calcitonin and a smaller response to cautery of the thyroid gland, a procedure known to cause excessive release of endogenous calcitonin. Calcitonin content of the thyroid glands from rats of different ages did not differ significantly.
However, since the oldest rat had larger thyroid glands, a significantly greater amount of calcitonin was found in the total thyroid glands of these rats.
The release of calcitonin in response to hypercalcemia was not significantly different with advancing age.
In conclusion, the thyroid gland of old animals still able to restrict hypercalcemia and it was not an insufficient release of calcitonin that was a causative factor in the delayed recovery from hypercalcemia in older rats.