SUN-029 A Case of Successful Treatment of Hyponatremia due to SIAD with SGLT-2 Inhibitor Empagliflozin

Abstract Disclosure: W. Lewis: None. N. Chan: None. A.R. Gosmanov: None. Background: Therapy of hyponatremia due to syndrome of inappropriate antidiuresis (SIAD) in ambulatory setting can be challenging due to difficulties in persistent adherence to fluid restriction and lack of standardized pharmacological approaches aiming to restore sodium homeostasis. In complicated cases when conventional strategies are exhausted, correction of hyponatremia in such patients may require additional measures. In this regard, there is early evidence that off-label use of SGLT-2 inhibitors added to maximal fluid restriction measures can modestly improve serum sodium (SNa) in SIAD patients. Clinical presentation: A 67-yo Caucasian male with history of laryngeal and esophageal squamous cell carcinoma in remission, hypothyroidism, and a 40-year smoking history was referred to endocrinology clinic for evaluation of chronic hyponatremia. Patient was known to have chronically mildly reduced SNa levels in 130-134 (135-145 mEq/L) range; however recent assessments in primary office showed unexplained SNa decrease to 122 mEq/L. In endocrinology clinic, weight was 69.5 kg, blood pressure was 152/78 mmHg, he was euvolemic on examination and not on medications that could affect SNa. Extensive laboratory evaluation revealed serum osmolarity of 279 (275-295 mOsm/kg), uric acid of 4.0 (3.5-7.8 mg/dL), serum cortisol at 8am of 16.4 (5-25 mcg/dL) and normal renal function, fasting glucose, lipid profile, liver tests and TSH along with spot urine Na of 46mEq/L and osmolarity 390 (350-900 mOsm/kg) suggesting that patient`s hyponatremia was due to SIAD. As prior recommendations to restrict fluid intake were not successful, we initiated oral NaCl 1g twice daily and furosemide 20mg daily and re-enforced the importance of fluid restriction. During follow up in 10 weeks, his SNa had not changed. In the setting of no meaningful improvements in SNa and emergence of new data showing modest therapeutic effects of SGLT-2 inhibitors in mild-to-moderate hyponatremia SIAD cases, we initiated empagliflozin 25 mg daily. Within one-week SNa increased from 125 to 127 mEq/L and to 137 mEq/L over 6 months period. This allowed us to initiate graded taper of NaCl and furosemide resulting in complete discontinuation of both medications over next 9 months while maintaining SNa in 134-136 mEq/L range with corresponding measured serum osmolarity in 279-294 mOsm/kg range. He remains eunatremic on empagliflozin monotherapy. SGLT-2 inhibitor adherence was confirmed by pharmacy records and periodic monitoring of urinalysis that showed marked glucosuria. Empagliflozin use did not lead to any adverse effects. Conclusion: SGLT-2 inhibitors can improve SNa level in SIAD by promoting electrolyte-free water excretion while preserving solute balance. This case highlights potential utility of empagliflozin and SGLT-2 inhibitors in general as an adjunct therapy in patients with refractory hyponatremia due to SIAD. Presentation: Sunday, July 13, 2025