THE PHYSIOLOGY BEHIND DIABETES MELLITUS IN PATIENTS WITH PHEOCHROMOCYTOMA: A REVIEW OF THE LITERATURE

OBJECTIVE:This paper reviews the physiologic mechanisms responsible for glucose intolerance and diabetes mellitus in patients with pheochromocytoma. METHODS:Google Scholar and PubMed were searched using the following key words: "diabetes," "pheochromocytoma," "adrenoreceptors," and "hyperglycemia." All the articles that were retrieved and reviewed were in the English language. RESULTS:Glucose intolerance and diabetes mellitus, resulting from high circulating levels of catecholamines, are mainly the product of compromised insulin secretion from the β-cells in the pancreas, decreased glucose uptake in the peripheral tissues, and increased insulin resistance. CONCLUSION:As pheochromocytomas mainly present with cardiovascular and autonomic hyperfunctioning, it is important to understand the metabolic disorders associated with this rare disease. Hyperglycemia is an associated metabolic abnormality which can drastically improve after tumor resection, and significant downscaling of anti-hyperglycemic therapy is often required. ABBREVIATIONS:GLUT4 = glucose transporter type 4 HbA1c = hemoglobin A1c IL = interleukin OGTT = oral glucose tolerance test.