Insulin secretory capacity in newly diagnosed non-insulin dependent diabetics

Plasma insulin was measured fasting and after iv glucose in fifteen newly diagnosed non-grossly obese non-insulin dependent diabetics. Two-thirds had normal fasting insulin (less than 13 mU/L) and all had sub-normal responses to iv glucose. There was no significant correlation between fasting or stimulated insulin concentrations and body weight. Six subjects with totally "flat" response to iv glucose were tested after a standard 4MJ meal and after 75 g oral glucose. They now showed normal profiles of later phase insulin release to the meal test or oral glucose and a significant increase in early phase insulin concentration, but this response was still blunted when compared with control subjects. We conclude that for non-grossly obese NIDDs (1) insulin deficiency is a common and important disorder and (2) there may be a loss of beta cell sensitivity to blood glucose with retention of sensitivity to gut mediated factors.