The significance and interpretation of mildly abnormal oral glucose tolerance

Abstract

Intravenous glucose tolerance, release of immunoreactive insulin and the hypog'lycaemic response to exogenous insulin were investigated in nine normal, fifteen maturity-onset diabetic and twenty-five subjects (equivocal group) with a mild abnormality of oral glucose tolerance (Fasting blood glucose < 110 mg%, and two hour levels < 170 mg%). — Intravenous glucose tolerance (-KG.T.T.) and insulin sensitivity (KI.T.T.) of subjects in the equivocal group ranged from normal to low values, but were significantly different from the normal and frank diabetic groups. Within the equivocal group, eleven subjects had normal, eight diabetic and six borderlineKG.T.T. values. — Plasma insulin responses within the equivocal group varied widely: seven normal and seventeen typical diabetic responses occurred in individuals with either normal or reduced intravenous glucose tolerance. Despite this heterogeneity, a definite diagnosis was established in eleven of the twenty-five subjects with the present method of investigation. — Significant positive correlations were demonstrated both betweenKG.T.T. and plasma insulin andKG.T.T. and insulin sensitivity, suggesting that overall glucose tolerance is dependent on both insulin sensitivity and on the amount of circulating plasma insulin.