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 examined by euglycaemic hyperinsulinaemic clamps in ten patients with insulinoma. The "responders" (n = 5) and "non-responders" (n = 5) to diazoxide treatment were distinguished by using fasting plasma glucose and insulin concentrations. The index of insulin sensitivity was significantly decreased in pretreated "responders" as compared to healthy persons (19 +/- 3 vs 39 +/- 6 and 20 +/- 3 vs 37 +/- 5 mumol.kg-1.min-1 per mU.l-1 x 100, p < 0.01) and it was improved during diazoxide administration (27 +/- 4 vs 19 +/- 3 and 35 +/- 12 vs 20 +/- 3 mumol.kg-1.min-1 per mU.l-1 x 100, p < 0.05). Significantly decreased insulin sensitivity in pretreated "non-responders" (25 +/- 5 vs 39 +/- 6 and 28 +/- 6 vs 37 +/- 5 mumol.kg-1.min-1 per mU.l-1 x 100, p < 0.05) was not improved by diazoxide administration. Metabolic clearance rate of glucose was significantly higher in "non-responders" as compared to "responders" and healthy persons (12.7 +/- 3.4 vs 7.9 +/- 2.7 and 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 concentration, index of insulin sensitivity, and metabolic clearance rate of glucose and of insulin were normalized after surgical removal of an insulinoma in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)