Calcitonin from ultimobranchial glands of dogfish and chickens.

Acid extracts of thyroid glands from a small shark Squalus suckleyi and domestic fowl Gallus domestica contained no detectable calcitonin activity, while very potent hypocalcemic responses were obtained in rats with similar extracts from the ultimobranchial glands of these two species. The calcitonin concentration was 4 to 40 times that present in hog thyroid, which, as in most other mammals, contains ultimobranchial tissue. The evidence suggests that calcitonin is a fundamental calcium-regulating hormone present in all higher vertebrates and that it is an ultimobranchial rather than a thyroid hormone. It also indicates an important and hitherto unrecognized function for the ultimobranchial glands.