Hyponatremia is a decrease in sodium ions in the blood due to various reasons, and the common causes are divided into three categories: 1. Inadequate salt intake, too little salt in the body by mouth or intravenously, for example, gastrointestinal disorders, inability to eat by mouth or coma, requiring intravenous rehydration, and insufficient sodium chloride supplementation.2. Increased salt excretion, massive vomiting, diarrhea, excessive sweating, or cranial brain injuries, and cerebral salt depletion syndrome occurs after pituitary gland surgery, and sodium chloride is excreted more from the urine. 3. Increased urinary excretion. 3, dilutional hyponatremia, such as cardiac insufficiency, resulting in decreased water excretion through the kidneys, leading to excess water in the body, causing dilutional hyponatremia. Traumatic brain injury or post-surgery, lung malignancy, carcinoid syndrome will cause inappropriate secretion of antidiuretic hormone syndrome, which will reduce water excretion through the kidneys, and dilutional hyponatremia will also occur.