Abstract: FR-PO0620
A Curious Case of Chronic Hyponatremia
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Clinical - 2
November 07, 2025 | Location: Exhibit Hall, 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
- Gardezi, Lemar Ahmad, VA Greater Los Angeles Healthcare System, Los Angeles, California, United States
- Lei, Sean, VA Greater Los Angeles Healthcare System, Los Angeles, California, United States
- Nikfar, Shaya, VA Greater Los Angeles Healthcare System, Los Angeles, California, United States
- Rhee, Connie, VA Greater Los Angeles Healthcare System, Los Angeles, California, United States
- Siu, Man Kit Michael, VA Greater Los Angeles Healthcare System, Los Angeles, California, United States
Introduction
Hyponatremia, defined as a serum sodium level <135 mEq/L, is a common electrolyte abnormality frequently encountered in clinical practice. Chronic cases often stem from hormonal imbalances, medication side effects, excessive fluid intake, poor dietary habits, or psychological disorders. A substantial portion of chronic hyponatremia cases are due to Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH), a diagnosis reached after excluding other causes. Within SIADH, reset osmostat syndrome represents a distinct and underrecognized subtype.
Reset osmostat syndrome is characterized by an altered threshold for ADH secretion. Normally, ADH release is finely tuned by serum osmolality to maintain sodium levels within a narrow range. In reset osmostat, this regulatory set point is chronically lowered, resulting in persistent hyponatremia. This can occur in response to conditions such as malignancy, infection, or neurological conditions. Despite low sodium levels, patients often remain asymptomatic and do not exhibit typical hyponatremic symptoms like confusion, seizures, or fatigue.
Case Description
We present the case of a 47-year-old man with a 20-year history of SIADH. The cause of his hyponatremia remained unclear, prompting a long-term management plan involving salt tablets (up to 2g TID) and strict fluid restriction (<1L/day). During a recent hospital admission, a water-loading test revealed appropriate urinary dilution and output, consistent with reset osmostat syndrome. As a result, restrictive interventions were discontinued, and the patient is now being monitored without salt tabs or fluid restriction.
Discussion
Management of reset osmostat syndrome differs significantly with other forms of chronic hyponatremia. Conventional SIADH treatments include fluid restriction, sodium supplementation, and medications like urea or vasopressin antagonists. In reset osmostat, these interventions may be unnecessary, or even harmful. Because the body has adapted to a lower sodium set point, aggressive correction can lead to complications such as osmotic demyelination syndrome. Accordingly, treatment focuses on careful monitoring and avoiding overcorrection.
This case highlights the importance of appropriate diagnosis, particularly in longstanding cases, to ensure appropriate and safe management. Though rare, reset osmostat syndrome demands a nuanced understanding and approach.