Disturbances of glucose metabolism are observed in many endocrinopathies as an effect of enhanced secretion of counter- -regulatory hormones, such as growth hormone, catecholamines, glucocorticosteroids, aldosterone and glucagon. In patients with pheochromocytoma, impaired glucose tolerance results from multiple mechanisms, mainly from inhibition of insulin secretion, stimulation of gluconeogenesis and glycogenolysis, as well as enhanced lipolysis. Increased glucose levels are observed in 50% of patients with pheochromocytoma, while diabetes is diagnosed in 15-48% of cases. Patients usually show the features of type 2 diabetes and do not require insulin treatment. Administration of a-adrenergic drugs before operation does not significantly improve carbohydrate tolerance but after tumour resection full retreat of diabetes symptoms is observed.