Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
Basics
The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a disorder with impaired water excretion (concentrated urine), caused by abnormal production of antidiuretic hormone (ADH) despite low serum osmolality.
Description
- 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 pulmonary disorder or central nervous system (CNS) disease
- Common cause of hyponatremia in hospitalized patients
- Synonym(s): SIADH; syndrome of inappropriate antidiuresis
Epidemiology
Incidence
- Often found in the hospital setting, especially perioperative patients in response to stress, intravenous fluids, and drugs; the 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., risperidone, quetiapine, phenothiazines, haloperidol)
- Analgesics (e.g., duloxetine, pregabalin, tramadol, NSAIDs)
- Anticonvulsants (e.g., carbamazepine, oxcarbazepine, valproic acid, phenytoin)
- Others (e.g., vasopressin, DDAVP, oxytocin, ciprofloxacin, α-interferon, ecstasy)
- Malignancies (ectopic ADH production):
- Bronchogenic or small cell carcinoma of the lung
- Lymphoma
- Mesothelioma
- Pancreatic adenocarcinoma
- Thymoma
- Pulmonary conditions:
- Asthma/COPD
- Atelectasis/pneumothorax
- Cystic fibrosis
- Positive pressure mechanical ventilation
- Pneumonia (viral, bacterial)
- Pulmonary tuberculosis (TB)
- Sarcoidosis
- Neurologic causes:
- Brain tumor
- CNS injury (i.e., subarachnoid hemorrhage, trauma, stroke, surgery)
- CNS lupus
- Encephalitis, meningitis
- Epilepsy
- Guillain-Barré syndrome
- Multiple sclerosis
- Acute intermittent porphyria
- Delirium tremens
- HIV infection/AIDS
- Rocky Mountain spotted fever
Genetics
- 10% of patients have an X-linked mutation of vasopressin V2 receptor (V2R).
- Polymorphisms in TRPV4 gene
Risk Factors
- Advanced age
- Postoperative status
- Institutionalization
- Use of predisposing drugs
General Prevention
Avoid high-risk medications, if drug induced.
Commonly Associated Conditions
See “Etiology and Pathophysiology.”
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Citation
Domino, Frank J., et al., editors. "Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688244/all/Syndrome_of_Inappropriate_Antidiuretic_Hormone_Secretion__SIADH_.
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH). In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688244/all/Syndrome_of_Inappropriate_Antidiuretic_Hormone_Secretion__SIADH_. Accessed November 21, 2024.
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH). (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688244/all/Syndrome_of_Inappropriate_Antidiuretic_Hormone_Secretion__SIADH_
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 November 21]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688244/all/Syndrome_of_Inappropriate_Antidiuretic_Hormone_Secretion__SIADH_.
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