SIADH; Syndrome of inappropriate antidiuretic hormone secretion
Antidiuretic hormone (ADH), or vasopressin, is a substance produced naturally by the hypothalamus and released by the pituitary gland. The hormone controls the amount of water your body removes.
Ectopic ADH secretion is the release of ADH from an abnormal location within the body. Ectopic means "out of place."
The most common cause of ectopic ADH secretion is cancer. Certain lung cancers, as well as some head and neck tumors, are the most common cancers that cause this problem. In rare cases, many other tumors may cause ectopic ADH secretion.
The abnormal release of ADH makes it harder for the body to remove water. Fluid builds up in the body. Low blood sodium levels (hyponatremia) can occur.
Often, there are no symptoms from low sodium levels. However, changes in mental status and even seizures may occur.
Treatment is aimed at removing the cause of the problem (for example, surgery to remove a tumor producing ADH).
Limiting fluid intake is another common treatment. This helps prevent excess water from building up in the body.
Patients in the hospital with ectopic ADH that does not respond to other treatments may be given tolvaptan by mouth (orally) and conivaptan through a vein (intravenous). These treatments block the effects of ADH.
Lin M, Liu SJ, Lim IT. Disorders of water imbalance. Emerg Med Clin North Am. 2005;23(3):749-770.
Gagel RF. Endocrine manifestations of tumors: "ectopic" hormone production. In: Goldman L, Ausiello D, eds. Cecil Medicine. Philadelphia, PA: Saunders; 2007:chap 188.
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