Calcitonin and insulin secretion in normal man: study with somatostatin and calcium.

An increase in extracellular calcium concentration abolishes somatostatin-induced inhibition of insulin release from rat pancreas in vitro; since calcium fails to have a similar effect in vivo, and calcitonin (CT) is capable of inhibiting insulin release, we investigated calcium-stimulated CT secretion during somatostatin administration in normal human males. No significant differences between calcium-stimulated CT secretion during somatostatin infusion and in basal conditions were found. In addition, we confirmed that endogenous CT elicited by calcium administration significantly reduces basal insulin secretion. Thus, we suggest that calcium-induced CT release in vivo may counteract the reversal effect of calcium on the suppressor activity of somatostatin on insulin secretion as shown in vitro.