Abstract: TH-PO376
An Unexpected Cause of Hypokalemia and Metabolic Alkalosis
Session Information
- Fluid, Electrolyte, Acid-Base Disorders: Clinical - I
November 02, 2023 | Location: Exhibit Hall, Pennsylvania 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
- 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.