12215 A Rare Cause Of Cushing's Syndrome: Acth-producing Pheochromocytoma

Abstract Disclosure: S. Jimenez Salazar: None. C. Aguilar Londoño: None. N. Aristizabal Henao: None. N. Buitrago Gómez: None. S. Saldarriaga Betancur: None. D.L. Beltran: None. J.L. Torres: None. Background: Cushing's syndrome is a severe endocrine disorder caused by chronic, autonomous, and excessive cortisol secretion. Among all causes, ectopic ACTH production continues to be one of the most challenging diagnoses. Rarely, pheochromocytomas secrete hormones other than catecholamines, including ACTH and CRH. The secretion of these hormones can alter the clinical presentation and make the diagnosis more difficult. Clinical Case: A previously 60-year-old woman with hypertension and no other relevant medical history presented with unintentional weight loss of 16 kg and constipation. Physical examination revealed a moon face, supra-labial and chin facial hair. Laboratory studies demonstrated hypokalemia (potassium 3.02 mEq/L, n: 3.5-5 mEq/L) and newly diagnosed diabetes (HbA1c 8.69%, n <5.7% and fasting glucose 282 mg/dL, n: 70-100 mg/dL), both difficult to control. Considering the clinical and biochemical findings, hypercortisolism was evaluated by measuring 24-hour urinary free cortisol (1853 mcg/24h, n: 4-176 mcg/24h), nocturnal serum cortisol (40.9 mcg/h, n:<7.5 mcg/h), and 1 mg dexamethasone suppression test (43.1 mcg/h, n:<1.8 mcg/h), confirming cortisol excess. ACTH was measured (95 pmol/mL, n: 4.7-48.5 pg/mL) suggesting ACTH-dependent cause, leading to a dynamic test with high doses of dexamethasone (8mg) with suppression greater than 50% and normal pituitary MRI, both compatible with an extrahypophyseal cause. Peripheral imaging evaluation was conducted with cervical-thoracic CT scan and abdominal MRI confirming the presence of a complex adrenal mass. Among adrenal hyperfunction studies, primary hyperaldosteronism was ruled out (Aldosterone 9.8 ng/dL, n: 1-32 ng/dL and Plasma Renin Concentration 1.1 ng/dL, n: 0.16-2.3 ng/dL), and pheochromocytoma was confirmed (Normetanephrines 2725.4 mcg/24h, n: 0-600 mcg/24h and Metanephrines 1550 mcg/24h, n: 0-350 mcg/24h). Considering the described adrenal lesion with biochemical behavior, the possibility of ectopic ACTH production from pheochromocytoma was studied. Therefore, ketoconazole 200mg every 8 hours was initiated for hypercortisolism control and adrenergic blockade protocol as pre-surgical preparation for adrenalectomy. Potassium levels (4.48 mEq/L, n: 3.5-5 mEq/L) and glucose levels (93 mg/dL, n: 70-100 mg/dL) normalized after the procedure. Pathology and immunohistochemistry confirmed the diagnosis of an ACTH-producing pheochromocytoma. Conclusion: Pheochromocytoma is a rare cause of ectopic ACTH secretion where pre-surgical management of catecholamine excess and hypercortisolism is crucial, and adrenalectomy is often curative. Reference: (1) Elliott PF, Berhane T, Ragnarsson O, Falhammar H. Ectopic ACTH- and/or CRH-Producing Pheochromocytomas. J Clin Endocrinol Metab 2021;106:598-608. Presentation: 6/1/2024