Somatostatin inhibits the pentagastrin-induced release of serum calcitonin in medullary carcinoma of the thyroid.

The effect of somatostatin on the secretion of calcitonin was studied in four patients with medullary carcinoma of the thyroid (MCT). The basal serum calcitonin level was markedly elevated in all cases. A bolus injection (100 microgram) of somatostatin followed by an intravenous infusion (5 microgram/min) for 60 min suppressed the basal calcitonin level in three of the four patients by 24-42%, while it had no inhibitory effect in one case. In another experiment, the pentagastrin-stimulated (6 microgram/kg s.c.) calcitonin release was partially blocked by a simultaneous i.v. injection of somatostatin (200 microgram) in all four patients studied. These experiments add human calcitonin to the list of hormones whose release in inhibited by somatostatin.