Glucagon secretion in patients with hypoparathyroidism: effect of serum calcium on glucagon release

The aim of the present study was to evaluate the influence of changes in the serum calcium concentration upon glucagon secretion in man. For this purpose, a group of subjects with either idiopathic (four cases) or secondary (two cases) hypoparathyroidism was submitted to an arginine test (0.5 g/kg) before and after the correction of hypocalcemia. In the presence of hypocalcemia, the glucagon response to the amino acid was modest and delayed (glucagon peak, 150 +/- 28 pg/ml). The acute correction of hypocalcemia produced a striking increase in basal glucagon levels (125 +/- 24 vs. 75 +/- 15 pg/ml; P less than 0.01) and restored the glucagon peak in response to arginine (270 +/- 50 pg/ml; P less than 0.01). The increase in plasma glucose triggered by arginine was augmented under normocalcemic conditions, while the pattern of plasma insulin response was quite similar. These results indicate that glucagon secretion in man is critically dependent on the serum calcium concentration.