Glucose intolerance occurs in about 30% of patients with pheochromocytoma, but overt diabetes mellitus is uncommon.182 Mechanisms responsible for glucose intolerance include suppression of insulin by α-adrenergic receptor stimulation of β cells; an increase in insulin resistance, probably related to elevated plasma free fatty acid levels; and increased hepatic glucose output as a result of β-adrenergic stimulation of hepatocytes. α-Adrenergic receptor blockade improves glucose tolerance and insulin secretion.
The glucose tolerance test, also known as the oral glucose tolerance test, measures your body's response to sugar (glucose). The glucose tolerance test can be used to screen for type 2 diabetes. More commonly, a modified version of the glucose tolerance test is used to diagnose gestational diabetes — a type of diabetes that develops during pregnancy.