Pheochromocytoma-Induced Hyperglycemia Leading To Misdiagnosis Of Type 1 Diabetes Mellitus

ABSTRACT Objective: We describe a young patient who had hyperglycemia as a sign of pheochromocytoma. He had been diagnosed with type 1 diabetes, but insulin was ultimately discontinued. We also examine the impact of metyrosine on glucose levels during the perioperative period of adrenalectomy. Methods: We present a case report with clinical, imaging, and laboratory findings and provide a brief review of the literature. Results: A 31-year-old man presented with uncontrolled hypertension. His urinary metanephrine levels were very high (metanephrine 51,460 μg/24 hours; normetanephrine 17,666 μg/24 hours). Magnetic resonance imaging revealed bilateral enlarged adrenal glands (left 6.5 × 6.0 × 5.7 cm; right 8.3 × 8.4 × 7.9 cm) and he was diagnosed with pheochromocytoma. In preparation for bilateral adrenalectomy, his blood pressure was controlled with phenoxybenzamine and metyrosine. Glucose levels and exogenous insulin declined with metyrosine therapy. The patient was determined to have multiple endocrine neoplasia type 2A syndrome. He had been misdiagnosed with type 1 diabetes mellitus with negative anti–glutamic acid decarboxylase 65. Conclusion: Excess catecholamine production can lead to hyperglycemia, which may be reduced with use of metyrosine. During the pre-operative preparation, glucose and insulin requirements should be carefully monitored to reduce the risk of hypoglycemia before and after pheochromocytoma resection. Abbreviation: MEN2A = multiple endocrine neoplasia type 2A