Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) is a topic covered in the 5-Minute Clinical Consult.

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  • A syndrome of abnormal production of antidiuretic hormone (ADH), despite low serum osmolality, leading to hyponatremia and inappropriately elevated urine osmolality
    • Decreased urinary electrolyte-free water excretion leads to dilutional hyponatremia (total body sodium [Na] levels may be normal or near normal, but the patient’s total body water is increased).
    • Often secondary to medications but may be associated with an underlying disorder, such as neoplasm, pulmonary disorder, or CNS system disease
  • Synonym(s): syndrome of inappropriate secretion of ADH; syndrome of inappropriate antidiuresis


  • Often found in the hospital setting, where incidence can be as high as 35%
  • Predominant age: elderly
  • Predominate sex: females > males

Etiology and Pathophysiology

  • Drugs:
    • Antidepressants (e.g., SSRIs, tricyclics, monoamine oxidase inhibitors [MAOIs]),
    • Antineoplastic drugs (e.g., vincristine, vinblastine, cisplatin, cyclophosphamide)
    • Antipsychotic agents (e.g., phenothiazines, thioridazine, haloperidol)
    • Analgesics (e.g., NSAIDs)
    • Antiepileptics (e.g., carbamazepine, oxcarbazepine, valproic acid)
    • Oral hypoglycemics (e.g., chlorpropamide, metformin)
    • Others (e.g., vasopressin, DDAVP, oxytocin, ciprofloxacin, α-interferon, ecstasy)
  • Neoplasms (ectopic ADH production):
    • Bronchogenic carcinoma
    • Small cell carcinoma of the lung
    • Oat cell carcinoma of the lung, mesothelioma
    • Pancreatic carcinoma
    • Hodgkin disease
    • Thymoma
  • Pulmonary conditions:
    • Asthma/COPD
    • Atelectasis
    • Cystic fibrosis
    • Positive pressure mechanical ventilation
    • Pneumonia
    • Pulmonary tuberculosis (TB)
    • Sarcoidosis
  • Neurologic causes:
    • Acute porphyria
    • CNS injury (i.e., SAH, trauma, stroke)
    • CNS lupus
    • Encephalitis
    • Epilepsy
    • Guillain-Barré syndrome
    • Meningitis
    • Multiple sclerosis
  • Other:
    • HIV infection
    • Hypothyroidism, myxedema
    • Rocky Mountain spotted fever
  • Idiopathic

  • 10% of patients have X-linked mutation of V2R.
  • Polymorphisms in TRPV4 gene

Risk Factors

  • Use of predisposing drugs
  • Advanced age
  • Postoperative status
  • Institutionalization

General Prevention

  • Search for cause, if unknown.
  • Reduce/change medications, if drug-induced.
  • Lifelong restriction of fluid intake

Commonly Associated Conditions

See “Etiology and Pathophysiology.”

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TY - ELEC T1 - Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) ID - 816889 ED - Baldor,Robert A, ED - Domino,Frank J, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -