A Comparative Analysis of Insulin Sensitivity, β-cell Function and Glucose Effectiveness in Endocrine Disorders with Excess Counter Regulatory Hormones and in Type 2 diabetes

Abstract

Frequent samplings of WGTT and Bergman's minimal model analysis were performed in 12 patients with Cushing's syndrome, 6 with acromegaly, 6 with pheochromocytoma, and 33 with type 2 diabetes to elucidate the mechanisms underlying glucose intolerance. Nineteen healthy young volunteers served as controls. Insulin sensitivity (S_I) was low in patients with Cushing's syndrome, acromegaly, and type 2 diabetes but normal in patients with pheochromocytoma. The acute insulin response to glucose (AIR) was lower than normal in patients with acromegaly, pheochromocytoma and type 2 diabetes. A compensatory increase in the AIR, which might be expected, was absent in patients with Cushing's syndrome. Glucose effectiveness (S_G) was normal in all endocrine disorders but impaired in type 2 diabetes. We concluded that insulin resistance and the failure of the β-cell compensatory mechanism contribute to glucose intolerance in Cushing's syndrome and acromegaly, while deficient insulin secretion plays a major role in pheochromocytoma. The coexistence of insulin resistance, β-cell failure and impaired S_G are characteristic of type 2 diabetes.