Calcitonin activity of the thyroid gland in primary hyperparathyroidism.

The thyroidal content of calcitonin was investigated in patients with euthyroid goitre, patients undergoing laryngectomies or neck operations and finally patients with primary hyperparathyroidism using method of biological titration. Patients with primary hyperparathyroidism had markedly decreased content of calcitonin in the thyroid gland when compared with the content of calcitonin of both groups of patients without calcium metabolism disturbance. Decreased content of calcitonin in patients with primary hyperparathyroidism can be explained by long lasting hypercalcaemia during which the rate of biosynthesis of calcitonin in the C cells does not keep up with the rate of release of calcitonin into the circulation.