INS and diabetes mellitus: The mechanism of pheochromocytoma-induced diabetes is related to insulin resistance and suppression caused by excess catecholamines.2 Through activation of hepatocyte β and α receptors, inhibition of insulin secretion in β cells of the pancreas, and blockade of GLUT4 transporters in muscle and adipose, catecholamines secreted in pheochromocytomas increase glycogenolysis and gluconeogenesis while interfering with normal feedback control of insulin.3