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Abstract: PO1469

Hypokalemia from ACTH-Secreting Pheochromocytoma

Session Information

Category: Trainee Case Report

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Shaikh, Sana J., Barnes-Jewish Hospital, Saint Louis, Missouri, United States
  • Vijayan, Anitha, Washington University in Saint Louis, Saint Louis, Missouri, United States
  • Mutneja, Anubha, Washington University in Saint Louis, Saint Louis, Missouri, United States
Introduction

The kidney is the critical effector organ in potassium homeostasis and mineralocorticoids (MC, usually aldosterone), distal sodium delivery and urine flow impact its response. Hypokalemia with HTN and metabolic alkalosis points to high MC activity. This can be classified as (a) ↑renin ↑aldosterone (b) ↑aldosterone despite ↓renin or (c) ↓renin ↓aldosterone. Here we describe an unusual case of hypokalemia due to ACTH-secreting pheochromocytoma.

Case Description

62-year-old man with resistant HTN, DM, multiple sclerosis was admitted for persistent hypokalemia. Medications were KCL 360 mEq/day, amlodipine, carvedilol, doxazosin, hydralazine and lisinopril. Labs showed hypokalemia (2.4 mmol/L) and metabolic alkalosis (HCO3 31 mmol/L). Urinary potassium losses were significant. After aldosterone level returned low, focus shifted towards hypercortisolism as a cause of MC activity. Studies confirmed raised cortisol and high ACTH. Pituitary gland workup was negative. Investigation for ectopic ACTH production revealed bilateral adrenal hyperplasia and discrete left adrenal mass. Adrenal hormone workup detected raised catecholamines. Adrenal vein sampling for ACTH showed laterization to the left. After alpha and beta-blockade, laparoscopic left adrenalectomy was done. Intraoperative biochemistry and pathology confirmed ACTH-secreting pheochromocytoma.

Discussion

In the distal nephron, cortisol is inactivated to cortisone by 11-beta-dehydroxysteroid dehydrogenase 2 (11βHSD2). Hypercortisolism causes relative deficiency of 11βHSD2 due to enzyme saturation. Cortisol then stimulates non-selective MC receptor.

Systematic workup led to diagnosis of ACTH-secreting pheochromocytoma. After resection of ectopic ACTH source, patient became normokalemic and was discharged with steroid replacement.