Insulin secretion after oral calcium load.

Oral glucose tolerance test with 50 g glucose was carried out with and without simultaneous oral administration of 3 g calcium lactate. Blood sugar and serum immunoreactive insulin (IRI) were measured before and 30, 60, 90 and 120 min after glucose load in 11 diabetics and 11 non-diabetics. Similar oral glucose tolerance test was performed with and without intravenous administration of 10 ml 8.5% calcium gluconate in 6 diabetics and 6 non-diabetics. Maximum serum level after glucose load (Max IRI), maximum rise of serum IRI following glucose load (Max delta IRI), maximum delta IRI/delta BS following oralglu cose load (Max delta IRI/delta BS), the area surrounded by the delta IRI curve and the abscissa (sigma delta IRI) and the area surrounded by the delta IRI/delta BS curve and the abscissa (sigma delta IRI/delta BS) significantly increased in diabetics but not in non-diabetics after oral calcium load, whereas intravenous calcium load failed to influence any of these values. Oral calcium load thus appears to augment glucose-induced insulin secretion only in diabetics, suggesting some abnormality in the mechanism of insulin secretion with reference to calcium in diabetes mellitus.