Abstract: SA-PO0619
Ectopic ACTH Syndrome Presenting as Refractory Renal Potassium Wasting in Metastatic Uterine Neuroendocrine Carcinoma
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 2
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Rjob, Ashraf S., The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
- Obole, Eshetu L., The Ohio State University Wexner Medical Center, Columbus, Ohio, United States
Introduction
Ectopic ACTH syndrome (EAS) can present as a nephrology emergency. Cortisol excess saturates 11β-HSD2, producing apparent mineralocorticoid excess with hypokalemia, alkalosis, and hypertension despite suppressed aldosterone. Steroidogenesis inhibitors reverse kaliuresis but risk adrenal insufficiency, especially with concurrent CYP3A4-inhibiting azoles.
Case Description
A 75-year-old woman with metastatic uterine large-cell neuroendocrine carcinoma presented with hypertensive urgency and hypokalemia (K 2.1 mmol/L) with metabolic alkalosis (CO2 36 mmol/L). Despite aggressive repletion and potassium-sparing therapy, renal K wasting persisted (urine K 66.3 mmol/L). Aldosterone was suppressed (4 ng/dL). AM cortisol was 77.1 mcg/dL, ACTH 81.7 pg/mL; cortisol was unsuppressed after high-dose dexamethasone. Pituitary MRI was unremarkable. CT/PET and pleural cytology confirmed metastatic neuroendocrine carcinoma, establishing EAS. Spironolactone, amiloride, potassium, and ketoconazole improved K and BP (Figure). She transitioned to osilodrostat; voriconazole was added for aspergillosis. Within weeks, K shifted to hyperkalemia (6.4 mmol/L) with hyponatremia (Na 121 mmol/L) from converging mechanisms: osilodrostat blockade, voriconazole-induced CYP3A4 inhibition raising osilodrostat levels, azole adrenal suppression, and potassium-sparing agents (Figure). Electrolytes normalized after glucocorticoid supplementation, holding osilodrostat, and stopping potassium-sparing therapies.
Discussion
This case illustrates EAS as a nephrology diagnosis with cortisol-driven apparent mineralocorticoid excess causing hypertension, alkalosis, and kaliuresis despite suppressed aldosterone. The rapid shift from refractory hypokalemia to life-threatening hyperkalemia highlights bidirectional electrolyte risks when steroidogenesis inhibitors are compounded by CYP3A4-inhibiting azoles, requiring close monitoring and early de-escalation.