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Abstract: FR-PO701

Hyponatremia due to Primary Adrenal Insufficiency Treated by Cortisol Replacement

Session Information

Category: Trainee Case Report

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Khalid, Sheikh Bilal, University of North Carolina, Chapel Hill, North Carolina, United States
  • Hladik, Gerald A., University of North Carolina, Chapel Hill, North Carolina, United States
  • Saha, Manish K., UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Kanu, Obiajulu, UNC Hospitals, Chapel Hill, North Carolina, United States
Introduction

Hyponatremia complicating malignancy is most commonly seen due to the syndrome of inappropriate antidiuretic hormone secretion. We present a unique case in which metastatic non-small cell lung cancer (NSCLC) led to primary adrenal insufficiency and hyponatremia

Case Description

A 66-yr-old man was admitted for symptomatic hyponatremia. He was evaluated at an outside facility for a month history of blood-streaked sputum and weight loss. He was hypotensive with initial serum sodium (SNa) 125 mEq/L,potassium 5.3 mEq/L,bicarbonate 22 mEq/L,chloride 86 mEq/L and Creatinine 0.5 mg/dL. After receiving 1 L of normal saline,he became confused with an associated fall in SNa 116 mEq/L,prompting transfer to our institution. On arrival,he was lethargic and disoriented. His vital signs were normal.Physical examination revealed a disoriented man with digital clubbing. Laboratory studies revealed a serum osmolality 235 mOsm/kg,urine osmolality (UOsm) 271 mOsm/kg and urine sodium 74 mmol/L. CT of head showed superior cerebellar mass with vasogenic edema. Further imaging revealed right upper lobe lung mass and bilateral adrenal nodules. He was treated with dexamethasone 6 mg every 6 hours for vasogenic edema and suspicion for adrenal insufficiency. Repeat laboratory studies showed improvement of SNa to 123 mEq/L and decrease in UOsm to 129 mOsm/kg. The SNa decreased to 120 mEq/L while the UOsm increased to 382 mOsm/kg after tapering of dex. A cosyntropin stimulation test was consistent with primary adrenal insufficiency. Hydrocortisone therapy at replacement doses resulted in normalization of SNa

Discussion

Adrenal glands are commonly involved in metastatic cancer but primary adrenal insufficiency uncommonly ensues, unless majority of the adrenal cortex is destroyed. Although it has been reported with advanced breast cancer and colon carcinoma, to our knowledge only a handful of cases of adrenal insufficiency leading to hyponatremia due to NSCLC have been reported. The pathogenesis is related to loss of negative feedback of cortisol on vasopressin which acts as a secretagogue for ACTH. The rate of rise of sodium is ideally 6-8 mEq/24 hours, but needs cautious monitoring since erratic changes may be seen (observed in our case). Dex is the initial corticosteroid of choice as it doesn’t interfere with cortisol assay during cosyntropin stimulation test