SUN-515 Severe Hyperglycemia As The Predominant Manifestation Of Pheochromocytoma: A Case Report

Abstract Disclosure: N.R. Brott: None. L. Kandimalla: None. A. Jawahar: None. Background: Pheochromocytoma (PCC) is a rare adrenal neuroendocrine tumor that produces excess catecholamines. PCC can classically present with a triad of episodic headache, diaphoresis, and tachycardia, although most do not. Here, we present an atypical case of PCC with normal vitals and severe hyperglycemia. Case Report: A 65-year-old female presented with vomiting and abdominal pain. She denied sweating, headaches, and palpitations. Vitals were notable for fluid-responsive hypotension and tachycardia. Labs showed blood glucose 411 mg/dL, A1C >15%, carcinoembryonic antigen 18.85 ng/ml (N: 0.1-5.0), metanephrine 2551 pg/ml (N: 0-88), and 24-hour urine metanephrine 11449 mcg/24h (N: 36-209). MRI showed a 6.4 cm centrally necrotic right adrenal mass. Following ten days of phenoxybenzamine, she had total resection of the right adrenal mass; pathology was consistent with PCC. Her course was complicated by preoperative hyperglycemia with robust insulin sensitivity, as well as post-operative shock and hypoglycemia without adrenal insufficiency requiring four days of vasopressors and continuous dextrose fluids. Discussion: In symptomatic patients with PCC, headache occurs in up to 90%, diaphoresis in up to 70%, and paroxysmal hypertension in up to 50%. Catecholamine excess can cause hyperglycemia, and hypoglycemia may follow resection due to abrupt withdrawal of catecholamines. Interestingly, this patient never demonstrated cardiovascular signs of catecholamine excess. Additionally, this case raises questions about the standard of care regarding preoperative alpha-blockade, as prolonged postoperative hypotension requiring vasopressors may be linked to its residual effects lasting up to four days, and studies have not shown clear evidence of benefit to morbidity or mortality in the context of modern surgical techniques. Further research into optimizing perioperative management of PCC is warranted. Conclusion: This case highlights an atypical presentation of pheochromocytoma with severe hyperglycemia but without classic signs or symptoms of catecholamine excess, such as episodic hypertension or headaches. The prolonged postoperative hypotension raises questions about the necessity of preoperative alpha-blockade in asymptomatic patients. This case underscores the importance of considering pheochromocytoma in patients with unexplained hyperglycemia and highlights the need for further research into optimizing perioperative management to minimize complications. Presentation: Sunday, July 13, 2025