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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


  • 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

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.


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.