SUN-500 Pheochromocytoma With Hypotension: A Clinical Conundrum

Abstract Disclosure: M. Bhalla: None. A. Gatiganti: None. D. Lovre: None. R. Galagan: None. Introduction: Pheochromocytomas (PCCs) are rare adrenal chromaffin-cell tumors that secrete catecholamines (CA), leading to diverse clinical presentations based on norepinephrine (NE), epinephrine (EPI), and dopamine (DA) levels. While NE excess typically causes hypertension (HTN), headaches (H/A), palpitations, and sweating, EPI-secreting PCCs can induce hypotension and syncope. Case Presentation: A 47-year-old female with past medical history of gastrointestinal stromal tumor (GIST) was seen in the Endocrinology clinic for recurrent episodes of postural dizziness and syncope. She reported bi-monthly spells of orthostatic dizziness and/or sudden syncope. She had occasional headaches, palpitations and sweating but denied chest pains. Exam showed BP 118/64 mmHg, HR 79 and no neurocutaneous stigmata. In an ER visit for postural dizziness, she experienced syncope upon standing, was treated with IV fluids and admitted to the hospital. Twenty-four hour urine metanephrines (MN), normetanephrines (NMN), EPI, NE and DA were normal (MN: 112µg/d (39-143 µg/d), NMN: 124 µg/d (109-393 µg/d), EPI: 6 µg/d (1-7 µg/d), NE 30 µg/d (16-71 µg/d) and DA 243 µg/d (77-324 µg/d)). She had an outpatient tilt-table test (TTT) which induced a postural syncopal episode with BP 87/44 mmHg, and a point of care blood draw revealed an elevated plasma EPI of 934 pg/ml (0-62 pg/ml) with normal NE 379 pg/mL (0-874 pg/ml). Additional lab results: normal ACTH stimulation test (30 minute cortisol 23.80 ug/dL ( >18 ug/dL), 60 minute cortisol 27.60 ug/dL) and chromogranin A of 27.7ng/mL (0-101.8 ng/mL). Holter and EKG tests were normal. Initial MRI and CT in 2020 showed normal adrenal glands, but an MIBG scan in 2021 revealed a 0.7 cm left adrenal nodule. PET DOTATATE in 2022 showed no abnormal uptake, while endoscopic ultrasound (EUS) confirmed the 0.7cm nodule. She underwent laparoscopic left adrenalectomy, with pathology confirming a 0.8 cm PCC. Postoperatively, her syncope resolved, but she gained 40 lbs over the ensuing 8 months and developed HTN. Conclusions: PCC typically presents with HTN and noradrenergic symptoms due to excess NE. Our patient atypically had orthostatic hypotension and syncope, driven by EPI excess relative to NE. Her hypotension was likely due to EPI binding β2 receptors in skeletal muscle, causing vasodilation and venous pooling. Episodic EPI surges were triggered by postural changes, as shown by normal baseline CA and an elevated EPI during the TTT-induced syncope. The small tumor escaped detection by MRI, CT and PET and was finally captured by MIBG and confirmed by EUS. Although PET DOTATATE is more sensitive imaging test for PCC, MIBG scan was diagnostic in our patient. The reversal of her hypermetabolic state following the surgery led to post-operative weight gain with hypertension. Genetic studies were negative for NF1, RET, SDHA, SDHAF2, SDHB, SDHC, SDHD, VHL, MEN1, TMEM127, MAX and FH. Presentation: Sunday, July 13, 2025