MON-007 The Need for Meticulous Management of Hyponatremia in a Patient with Central Diabetes Insipidus

Abstract Disclosure: S. Reyes: None. A. Makol: None. V. Kantorovich: None. Introduction: Challenges in management of central diabetes insipidus (CDI) are driven by dynamic balance between fluid intake, DDAVP dosing and physiologic processes affecting endogenous water metabolism (1). Tailored approach to individual needs and activities is essential for long term management, while deep understanding of processes causing acute sodium abnormalities. Clinical Case: A 36-year-old male with a history of recurrent pituitary germ cell tumor at age 7, post-chemotherapy and radiation, complicated by panhypopituitarism and CDI on replacement therapy that included DDAVP 0.1 mg PO TID. The hydration was achieved through two measured 400 ml drinks of water (during lunch and dinner), as well as some unaccounted amount during twice weekly intense exercises. Apparently, patient was adding additional DDAVP dose for nocturia, suggestive of unaccounted drinks. He presented with altered mental status, SNa 119 mEq/L, SOsm 256 mOsm/kg, UOsm715 mOsm/kg, high UNa and new increase in SCre. DDAVP was discontinued, fluid restricted to 750 ml/d and urea was added, leading to rapid overcorrection to SNa 141, correction of SOsm and dilution of urine, requiring IV D5W and DDAVP. Endocrinology was consulted as patient had persistent hyponatremia, increased creatinine, while on continued marked water restriction and periodic IV DDAVP. His DDAVP was switched to BID PO dosing, fluid restriction lifted to 1.5 l/d, while closely following SNa/SOsm/UOsm. Eight hours after the first PO dose and despite the expected changes in SOsm/UOsm, SNa/SCre did not improve until patient got repeat boluses of IV saline. Conclusion: Our patient presented with severe hyponatremia showing SIADH-like biochemistry, probably related to DDAVP overdose. With this said, persistent hyponatremia and persistent decrease in GFR strongly suggest concomitant chronic intravascular volume contraction, exaggerated by strict fluid restriction and, to lesser degree, sodium depletion. This suggests consideration of IV both volume and salt repletion in some of the cases. Overzealous overcorrection should be kept in mind and avoided in these cases. Overall, lack of thirst puts DI patients into position, where adjustable calculated water intake combined with either stable or also adjustable DDAVP dosing are pertinent for long term management, thus repeated education is needed across chronic management of DI. References: Verbalis, J. G., Goldsmith, S. R., Greenberg, A., Korzelius, C., Schrier, R. W., Sterns, R. H., & Thompson, C. J. (2013). Diagnosis, evaluation, and treatment of hyponatremia: Expert panel recommendations. The American Journal of Medicine, 126(10). Presentation: Monday, July 14, 2025