7305 Pheochromocytoma Presenting With Resistant Hyperglycemia

Abstract Disclosure: M. Economou: None. A. Devine: None. Background: Pheochromocytoma is a rare catecholamine producing tumor arising from the adrenal gland. Impaired glucose tolerance is a well-recognized hormonal and metabolic manifestation of pheochromocytoma caused by catecholamine excess [1]. Insulin resistance requiring very high doses of insulin in association with pheochromocytoma is, however, rare. Here we report a case of pheochromocytoma in a woman with diabetes mellitus that proved difficult to control despite high-dose insulin therapy. Case presentation: A 72-year-old woman with a longstanding history of type 2 diabetes mellitus, uncontrolled hypertension, hyperlipidemia and CVA presented to the hospital after she was found to have a hemoglobin of 7.0 ng/mL on routine labs. Notably, over the past 4 years, her insulin requirement gradually increased from 20 units/day to 50 units/day despite an A1c level of 6.1%. On presentation, our patient was hypertensive to 170/90 with limited response to multiple antihypertensive medications. Additionally, her glucose was severely uncontrolled, fluctuating between 200-500 mg/dL. Within days, the patient’s total daily insulin requirement increased tremendously to as much as 300 units/day. As part of her anemia workup, she underwent a contrast-enhanced CT abdomen & pelvis which identified a left adrenal mass measuring 2.2 x 2.8 x 2.9 cm. Further evaluation with MRI confirmed an adrenal mass suspicious for pheochromocytoma. Evaluation of plasma hormone levels revealed an elevated normetanephrine level of 7.10 nmol/L (normal: less than 0.89 nmol/L). Furthermore, the 24-h urinary normetanephrine level and chromogranin A levels were elevated to 145 mcg/day and 1203 ng/mL, respectively. Initial treatment with alpha and beta blockade improved blood pressure but glucose levels remained persistently elevated. The patient underwent left laparoscopic adrenalectomy and pathology revealed pheochromocytoma, measuring, 3.2 cm in diameter, with stains positive for CD56, synaptophysin and chromogranin. Surgical resection margins were negative for tumor. Postoperatively, insulin requirements returned to roughly that of her baseline, 40 units/day. Conclusion: Impaired glucose tolerance is a known phenomenon associated with pheochromocytoma. Despite this, it is unusual to see an insulin requirement rise as abruptly and drastically as seen in this case. Our patient, with relatively controlled diabetes had an enormous increase in her insulin requirement during her hospital course as evidenced by her insulin regimen which increased sixfold. This case highlights the importance of maintaining a high degree of suspicion for pheochromocytoma in patients with a sudden rise in insulin requirement and uncontrolled hypertension. Reference: (1) Ronen JA, Gavin M, Ruppert MD, Peiris AN. Glycemic Disturbances in Pheochromocytoma and Paraganglioma. Cureus. 2019 Apr 27;11(4): e4551. Presentation: 6/3/2024