GLUCOSE TOLERANCE AND IMMUNOREACTIVE INSULIN IN PATIENTS WITH PHEOCHROMOCYTOMA: THE EFFECT OF α-RECEPTOR BLOCKING AGENTS

Abstract

ABSTRACT Blood glucose, plasma insulin, free fatty acids and urinary noradrenaline were investigated in 5 patients with noradrenaline producing pheochromocytoma (4 adenomas, 1 metastatic tumour) and in 3 control subjects. Oral glucose tolerance tests were performed before therapy, during treatment with the α-receptor blocking agent phenoxybenzamine, and in 4 patients after surgical removal of the tumour. In the untreated pheochromocytoma patients, glucose curves were pathologically high; insulin secretion was low in relation to blood glucose levels or almost completely suppressed depending on the plasma noradrenaline concentrations. During phenoxybenzamine treatment glucose curves remained abnormal; insulin concentrations increased both in patients and control subjects. Six to 26 days after operation, glucose curves and insulin secretion became normal. Fractionated urine collections revealed a fall in noradrenaline excretion after oral glucose load. The urinary excretion of noradrenaline increased when α-receptor blockade was effective. The increased release of insulin under α-receptor blockade in patients and control subjects suggests that noradrenaline plays a role in the regulation of insulin secretion in normal conditions as well as in patients with pheochromocytoma.