What type of hyponatremia is often seen in patients with SIADH?

The correct identification of the type of hyponatremia seen in patients with Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH) is euvolemic hyponatremia. In SIADH, there is an excess secretion of antidiuretic hormone (ADH), which leads to water retention and dilution of serum sodium levels. However, patients typically do not exhibit signs of volume depletion or overload; rather, they maintain a normal fluid volume status, which is characteristic of euvolemic conditions.

In this scenario, despite the low serum sodium concentration, the total body water is increased, but the fluid status remains within normal limits, allowing for the classification as euvolemic hyponatremia. This makes it distinct from hypervolemic hyponatremia, where there would be signs of fluid overload, and hypovolemic hyponatremia, which is characterized by a loss of both sodium and water, leading to decreased total body fluid. Normovolemic hyponatremia is a term that can occasionally be used interchangeably with euvolemic hyponatremia, but it’s not as commonly utilized in clinical discussions as euvolemic