Inappropriate antidiuretic hormone (ADH) secretion, also known as syndrome of inappropriate antidiuretic hormone (SIADH), is a medical condition characterized by excessive secretion of ADH, which leads to increased water retention and dilutional hyponatremia (low sodium levels in the blood).
Normally, ADH is released in response to changes in blood volume or blood osmolality to increase water reabsorption in the kidneys and prevent dehydration. However, in SIADH, ADH is secreted inappropriately even when blood volume and osmolality are normal or high.
SIADH can be caused by a variety of underlying medical conditions, including tumors (especially lung cancer), infections, medications, and neurological disorders. It can also occur as a result of trauma or surgery.
Symptoms of SIADH include nausea, vomiting, headache, seizures, confusion, and decreased urine output. If left untreated, SIADH can lead to severe hyponatremia, which can cause seizures, coma, and even death.
Treatment for SIADH depends on the underlying cause and severity of symptoms. In some cases, simply discontinuing the medication or treating the underlying medical condition can resolve the condition. In more severe cases, treatment may involve fluid restriction, medications to increase sodium levels in the blood, and occasionally, surgery.