In which condition is euvolemic hyponatremia a typical manifestation?

Euvolemic hyponatremia is a condition characterized by low sodium levels in the blood while maintaining a normal blood volume. This state is often seen in specific medical conditions, primarily the Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH).

In SIADH, there is an excess production of antidiuretic hormone (ADH), which leads to increased water reabsorption in the kidneys, resulting in dilution of serum sodium. Even though the total body water increases, the extracellular fluid volume remains normal (euvolemic). This is distinct from other conditions that might cause hyponatremia alongside changes in volume status.

In contrast, conditions such as heart failure lead to fluid overload and subsequent dilutional hyponatremia, but with a characteristic increase in total body fluid volume—this represents a state of hypervolemia, not euvolemia. Hypovolemic shock involves actual volume depletion, resulting in a different mechanism of sodium imbalance. Lastly, adrenal insufficiency may lead to hyponatremia, but it is often associated with hypovolemia due to inadequate aldosterone secretion and salt wasting rather than maintaining a euvolemic state.

Therefore, SIAD