Dilutional hyponatremia (SIADH)

Alternative names:

SIADH; syndrome of inappropriate antidiuretic hormone secretion

Definition:

A disorder of fluid and electrolyte balance caused by excessive release of antidiuretic hormone (ADH).

Causes, incidence, and risk factors:

Fluid and electrolyte imbalance in this syndrome result from the inability to excrete dilute urine, retention of water within the body, and low sodium levels. The most common cause of SIADH is a type of lung cancer called "oat cell," which secretes excessive ADH. Other causes are pancreatic cancer, prostate cancer, Hodgkin's disease, central nervous system disorders, pulmonary disorders, certain drugs, thymomas, myxedema, and psychosis. SIADH may also develop in some children during the acute phase of meningitis. Risk factors are related to the causes. The incidence is 7 out of 10,000 people.