DIAGNOSIS OF INSULINOMAS BY SUPPRESSION TESTS

The decrease of insulin secretion in normal subjects in response to hypoglycaemia provides the basis for diagnostic suppression tests for insulinomas. Sixteen out of twenty patients with insulinomas had hypoglycaemia after an overnight fast, and an insulinoma could be diagnosed when the plasma-insulin levels were inordinately high in relation to the hypoglycaemia. Fish insulin was used to induce hypoglycaemia in twelve patients with insulinomas, four of whom had normal basal glucose levels after an overnight fast, and in all subjects suppression of endogenous insulin secretion was impaired. This dynamic suppression test provides a means of diagnosing or excluding an insulinoma as a cause of suspected hypoglycaemic attacks.