FRI200 Severe Cushing Syndrome Due To An ACTH-producing Pheochromocytoma

Disclosure: G.A. Stamatiades: None. A. Bikas: None. H.J. Shah: None. K. Wong: None. A. Vaidya: None. M. Nehs: None. S.S. Basaria: None. Background: Pheochromocytomas are rare catecholamine-secreting tumors that arise from sympathetic adrenomedullary chromaffin tissue. Rarely, pheochromocytomas co-secrete ACTH and patients present with Cushing syndrome. Due to its rarity, clinicians may not consider this etiology of Cushing syndrome. We report a case of a man with ACTH-producing pheochromocytoma in whom methodic systematic approach led to its diagnosis and successful treatment. Clinical Case: A 48-year-old man presented with altered mental status. His family confirmed depressed mood, paucity of thought, and occasional blank stares. The patient was diagnosed with type-2 diabetes mellitus and hypertension 3 months ago, which were not controlled despite being on multiple anti-hypertensives and anti-diabetic agents. His EEG, head CT, and brain MRI were normal. On admission, his laboratory tests were notable for hypokalemia (3.0 mmol/L, n<5.3 mmol/L) and metabolic alkalosis (HCO3 33 mmol/L, n<32 mmol/L). Physical examination showed facial plethora, multiple ecchymoses and profound proximal muscle weakness. CT scan of the abdomen showed a 3.4 cm left adrenal nodule with a density of 33 Hounsfield units and a 73% absolute washout. The right adrenal gland was hyperplastic. Plasma and urinary metanephrines were significantly elevated (plasma metanephrines 1.6 nmol/l, n < 0.50 nmol/l, urinary metanephrines 1,685 mcg/24h, n <646 mcg/24h). Midnight salivary cortisol was 11,500 ng/dl (n<100 ng/dl) and 24h urinary free cortisol was 13,099 mcg/24h (n < 45 mcg/24h). ACTH was 450 pg/ml (n<63pg/ml) with a serum cortisol of 93 ug/dl (n<18.4 ug/dl). His serum cortisol after 8 mg Dexamethasone Suppression test was 100 ug/dl. DOTATATE PET CT scan showed uptake in the left adrenal nodule. The workup was suggestive of left-sided pheochromocytoma producing ectopic ACTH. The patient underwent laparoscopic left adrenalectomy. Postoperative ACTH was undetectable, indicating surgical cure. His blood pressure and plasma glucose gradually improved and remained normal after discontinuation of all medications. Surgical pathology was consistent with pheochromocytoma with positive staining for ACTH, confirming the diagnosis of ACTH-producing pheochromocytoma. He was discharged home after successful rehabilitation. Clinical Lessons: Pheochromocytomas are a rare cause of ectopic ACTH production, resulting in clinical Cushing syndrome. Imaging of the contralateral adrenal gland provides a valuable clue in making the diagnosis of ectopic ACTH production (as the gland is enlarged rather than atrophic). Reference: (1) Elliott PF, Berhane T, Ragnarsson O, Falhammar H. Ectopic ACTH- and/or CRH-Producing Pheochromocytomas. J Clin Endocrinol Metab. 2021 Jan 23;106(2):598-608. doi: 10.1210/clinem/dgaa488. PMID: 32710791. Presentation: Friday, June 16, 2023