INSULIN ACTION IN PATIENTS WITH INSULINOMA INFLUENCED BY PHARMACOLOGICAL AND SURGICAL THERAPY

Organic hyperinsulinism due to insulinoma is accompanied by changes of insulin action on receptor and postreceptor levels. The influence of conservative and surgical treatment on insulin sensitivity was examine d by euglycaemic hyperinsulinaemic clamps in ten patients with insulin oma. The ''responders'' (n = 5) and ''nonresponders'' (n = 5) to diazo xide treatment were distinguished by using fasting plasma glucose and insulin concentrations. The index of insulin sensitivity was significa ntly decreased in pretreated ''responders'' as compared to healthy per sons (19 +/- 3 vs 39 +/- 6 and 20 +/- 3 vs 37 +/- 5 mu mol.kg(-1).min( -1)per mU.l(-1) x 100, p<0.01) and it was improved during diazoxide ad ministration (27 +/- 4 vs 19 +/- 3 and 35 +/- 12 vs 20 +/- 3 mu mol. k g(-1). min(-1) per mU.l(-1) x 100, p<0.05). Significantly decreased in sulin sensitivity in pretreated ''non-responders'' (25+/-5 vs 39+/-6 a nd 28+/-6 vs 37 +/- 5 mu mol.kg(-1).min(-1)per mU.l(-1) x 100, p<0.05) was not improved by diazoxide administration. Metabolic clearance rat e of glucose was significantly higher in ''non-responders'' as compare d to ''responders'' and healthy persons (12.7 +/- 3.4 vs 7.9 +/- 2.7 a nd 7.4 +/- 2.4 ml.min(-1).kg(-1), p<0.05) already in pretreated state. An inverse relationship was found between metabolic clearance rate of glucose and of insulin (r = 0.72, p<0.001). Plasma glucose, insulin c oncentration, index of insulin sensitivity, and metabolic clearance ra te of glucose and of insulin were normalized after surgical removal of an insulinoma in all patients. We conclude that euglycaemic clamps ma y be used in patients with insulinoma to consider the reliability of d iazoxide therapy.