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Kidney Week

Abstract: FR-PO288

Refractory Hypokalemia due to a Rare Paraneoplastic Syndrome

Session Information

Category: Onconephrology

  • 1700 Onconephrology

Authors

  • Ajaz, Aiman, Baylor College of Medicine, Houston, Texas, United States
  • Ajmal, Muhammad Suleman, Baylor College of Medicine, Houston, Texas, United States
Introduction

Renal potassium wasting can occur due to a variety of etiologies. Understanding the pathway resulting in potassium wasting is critical to treating and ultimately correcting the acid/base and electrolyte derangements seen in these cases.

Case Description

We present a case of a 54 year old female with newly diagnosed high grade metastatic neuroendocrine tumor (NET) admitted for intractable diarrhea improving after octreotide administration. Her labs, however, showed persistence of severe hypokalemia and metabolic alkalosis despite aggressive repletion. Urine electrolytes suggested renal potassium wasting with undetectable renin and aldosterone levels. Further workup showed elevated urine and serum cortisol levels with elevated adrenocorticotropin hormone (ACTH) which failed to be suppressed with dexamethasone suppression testing (DST), suggesting a paraneoplastic etiology for ACTH release. Due diligence was taken to ensure that ACTH release was not from a primary pituitary tumor by obtaining imaging and appropriate hormonal workup. It was determined that elevated cortisol exerts aldosterone-like effects on the mineralocorticoid (MRA) receptor resulting in renal potassium and hydrogen loss. The patient was started on spironolactone and ketoconazole in addition to oral potassium repletion with gradual improvements in serum potassium levels.

Discussion

As this case highlights, it is critical to understand the relationship between cortisol and the MRA receptor in addition to determining the cause for hypercortisolism which can be ACTH dependent or independent. Once it’s determined to be ACTH dependent, DST is performed. Failure to suppress cortisol with dexamethasone administration suggests paraneoplastic, autonomous ACTH release which can then stimulate cortisol synthesis in the adrenals via the steroid synthesis pathway. Cortisol, at high levels, acts upon the MRA receptor resulting in hypokalemic metabolic alkalosis. Targeting therapy by blocking the MRA receptor with spironolactone and inhibiting cortisol synthesis in the steroid synthesis pathway with ketoconazole ultimately lead to improvement in serum potassium levels in addition to oral repletion.