Somatostatin and Insulin Secretion in Man. IV. The Role of Calcium

In this study we evaluated the influence of changes in serum calcium concentration upon somatostatin-mediated inhibition of insulin secretion in man. For this purpose, we investigated the effect of somatostatin in a group of subjects with hypoparathyroidism before and after correction of hypocalcemia and in normal subjects made hypercalcemic by exogenous calcium administration. In the presence of hypocalcemia, somatostatin caused an almost total inhibition of glucose-induced insulin secretion. In addition, somatostatin significantly decreased glucose tolerance in those hypocalcemic patients who exhibited normal tolerance under basal conditions [glucose utilization (kG), 1.44 ± 0.13 before vs. 0.68 ± 0.14 during somatostatin; P ⁄ 0.02]. Glucose tolerance was unaltered in those subjects who had a decreased glucose tolerance under basal conditions (kG, 1.01 ±0.1 before vs. 0.88 ± 0.16 during somatostatin; P = NS). Under normocalcemic conditions, the insulin response to glucose and glucose tolerance were sign...