What condition is characterized by low serum sodium levels?

Hyponatremia is defined as a condition in which there is an abnormally low concentration of sodium in the serum, typically less than 135 mmol/L. Sodium is a crucial electrolyte that helps regulate water balance in the body, and its low levels indicate that there may be an imbalance of fluids, whether due to excess water retention, losses from the body, or an inadequate intake of sodium.

In contexts such as excessive fluid intake, certain medications, or underlying health issues like heart or kidney problems, the serum sodium can decrease significantly, leading to symptoms such as confusion, seizures, and in severe cases, coma. Understanding hyponatremia is essential for proper diagnosis and management of fluid and electrolyte imbalances.

Other conditions mentioned, such as hyperkalemia (high potassium levels), hypernatremia (high sodium levels), and hypokalemia (low potassium levels), focus on different electrolytes and their respective imbalances, which do not directly pertain to sodium levels. Thus, hyponatremia is the only condition from the list that specifically addresses low serum sodium levels.