ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on X

Kidney Week

Abstract: TH-PO376

An Unexpected Cause of Hypokalemia and Metabolic Alkalosis

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Haq, Kanza, Johns Hopkins University, Baltimore, Maryland, United States
  • Cervantes, Carmen Elena, Johns Hopkins University, Baltimore, Maryland, United States
  • Hanouneh, Tareq, Mayo Clinic in Florida, Jacksonville, Florida, United States
  • Hanouneh, Mohamad A., Johns Hopkins University, Baltimore, Maryland, United States
Introduction

Ectopic ACTH syndrome (EAS) is a rare cause of Cushing's syndrome and is often linked with cancer, particularly neuroendocrine tumors, among which bronchial carcinoids are the most common. ACTH-secreting pulmonary carcinoids are often small and pose diagnostic/therapeutic challenges.

Case Description

A 21-year-old man presented to the hospital with psychosis symptoms. His BP was 140/90 mmHg. Laboratory test results are listed in Figure 1A. Further workup revealed low serum levels of renin < 0.1 ng/ml/hour and aldosterone 3.1 ng/dL. AM serum cortisol, 24-hour urine cortisol, and ACTH levels were elevated at 49.5 mcg/dL, 5,904 ug/g Cr, and 258 pg/ml, respectively. Brain MRI showed a 5mm pituitary adenoma (Fig 1B). High-dose dexamethasone suppression test resulted in less than 50% suppression of serum cortisol, indicating a potential source of ectopic ACTH secretion. Inferior petrosal sinus sampling resulted in non-functional pituitary adenoma. A CT scan of the chest/abdomen/pelvis was performed but failed to identify the source of ACTH secretion. Eventually, a PET radiotracer (Gallium-68 dotatate) scan showed a left lung perihilar nodule with somatostatin receptor positivity (Fig 2A). Lung nodule resection confirmed a carcinoid tumor labeled immunohistochemically with ACTH and resulted in the resolution of hypokalemia and hypertension.

Discussion

11β-HSD2 enzyme inactivates cortisol to cortisone. High levels of circulating cortisol oversaturate the activity of 11β-HSD2, leading to a mineralocorticoid effect on the collecting ducts, causing sodium resorption and potassium excretion (fig 2B). Clinical manifestations of hypercortisolism include hypertension, hypokalemia, metabolic alkalosis, low serum renin, and low aldosterone levels.