Control of secretion of thyrocalcitonin in the rabbit as evaluated by radioimmunoassay.

Thyrocalcitonin was detected in the peripheral blood of the normal rabbit through the use of a recently developed sensitive radioimmunoassay for the hormone. Hormone was not detected in the plasma of thyroidectomized animals even after challenge with hypercalcemia. Studies on the rate of disappearance of injected thyrocalcitonin indicated that the turnover of the peptide in blood is rapid. Simultaneouschanges in hormone and blood calcium concentration were measured in 7 intact rabbits during calcium infusion. A directly proportional relationship between calcium and thyrocalcitonin concentrations was established. These findings support the concept that thyrocalcitonin is an important mammalian hormone. (Endocrinology 84: 36, 1969)