Studies of Thyrocalcitonin Action

Abstract

The hypocalcemic activity of thyroid extracts of hog, dog, lamb, deer and human origin were tested in Holtzman and Wistar rats and in dogs. All extracts except those of human origin were highly potent in Holtzman rats, reducing the plasma calcium concentration by an average of 0.8 to 1.0 mEq/l. The dog, deer and lamb extracts were comparably potent in Wistar rats but hog thyroid extracts gave variable responses. Similarly prepared extracts of 8 other dog tissues had no hypocalcemic activity in Holtzman rats. Adjustment of the pH of the thyroid extracts to 7.4 decreased their protein content from 7.0 to 3.5 mg/ml without loss of potency. In dogs, the animal thyroid extracts caused decreases in the plasma calcium concentration of 0.3 to 0.8 mEq/l and extracts of human thyroid were ineffective. Repeated administration of hog thyroid extracts, but not of extracts from other animal sources, caused progressively smaller decreases in the plasma calcium concentration. In the dog, the hypophosphatemic activity of thyroid extracts generally paralleled the hypocalcemic activity but no consistent effects on plasma magnesium concentrations occurred. (Endocrinology79: 131, 1966)