[Endogenous Production and Peripheral Utilization of Glucose in Patients with Insulinoma]

Endogenous glucose production (EGP), glucose clearance and insulin sensitivity were measured in 5 subjects with insulinoma before and 3 to 6 months after surgical resection of the tumour. Endogenous glucose production and glucose clearance were evaluated by infusion of [6,6 D2] glucose, and insulin sensitivity was determined by a euglycaemic hyperinsulinaemic glucose clamp. The patients served as their own controls. The postabsorption blood glucose level was low before treatment (0.51 +/- 0.01 g/l) and EGP was 1.86 +/- 0.10 mg kg-1 min-1 (normal value: 2.2 to 2.6 mg kg-1 min-1), whereas the insulin level was relatively high (16.4 +/- 1.6 mU/l). After surgical resection of the insulinoma, the blood glucose level rose to 0.94 +/- 0.02 g/l and EGP to 2.33 +/- 0.04 mg kg-1 min-1, whereas the insulin level fell to 6.4 +/- 0.5 mU/l. Glucose metabolic clearance in the fasting state was 3.68 +2- 0.21 mg kg-1 min-1 before and 2.46 +/- 0.09 (n = 2.44 to 3.46 ml kg-1 min-1) after surgery. Clamp dose-response curves were shifted to the left and insulin sensitivity was improved after surgery. These data suggest that chronic hyperinsulinaemia is associated with inhibition of endogenous glucose production, a rise in basal glucose clearance and a state of insulin insensitivity during the clamp.