Effects of Hypocalcemia and Theophylline on Glucose Tolerance and Insulin Release in Human Beings

Abstract

A study was carried out to investigate the role of serum calcium in the regulation of insulin secretion and glucose tolerance in response to an oral glucose load on human subjects in hypocalcemie and normocalcemic states. The subjects for this study comprised three groups. Group 1 consisted of 15 patients with hypoparathy-roidism. They were subjected to an oral glucose load, and blood samples were taken at 0, 30, 60, 90, 120, 150, and 180 minutes to determine the blood glucose and serum insulin levels. These patients were treated with vitamin D2; after normocalcemic states were achieved the same study was repeated. This group of patients showed an abnormal glucose tolerance test and a markedly reduced insulin release during their hypocalcemie state; these abnormalities returned to normal after treatment. Group 2 consisted of six patients with hypoparathyroidism and one patient with vitamin-D-resistant rickets. These patients were subjected to an oral glucose load and a theophylline infusion (1 gm. in three hours) when they were hypocalcemie. The theophylline infusion increased the insulin release to the level of control subjects' in spite of hypocalcemia. Ten healthy volunteers served as a control group (group 3). Our results indicate that serum calcium has an important role in glucose utilization by insulin release. This is the first experiment to be performed on human beings and shows that theophylline has a stimulatory effect on insulin secretion in the presence of hypocalcemia.