Investigation of insulin sensitivity in early diabetes. I. Procedure for the determination of insulin responsiveness in vivo.

Twenty-three normal weight subjects without any heredity of diabetes were characterized by a 2-hour glucose infusion test. All persons showed a normal carbohydrate tolerance and normal biphasic insulin secretion pattern. For the determination of insulin sensitivity a 1-hour priming dose--constant infusion technique was used. Two 30-minute-periods of insulin infusion (8 and 16 mU/kg, primed by a start injection of 1 and 2 mU/kg, respectively) provoked a decrease of plasma glucose and FFA concentrations by 35 +/- 12.5% and 55 +/- 30.2%, respectively. Values lower than 22.5% (glycemia) or 25% (FFA) indicate a diminished insulin responsiveness. The metabolic clearance rate of insulin did not change at several concentrations of IRI. Thus, the proposed procedure is suitable to study the insulin sensitivity in vivo.