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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Basics
Description
- 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 central nervous system (CNS) disease
- Synonym(s): syndrome of inappropriate secretion of ADH; syndrome of inappropriate antidiuresis
Epidemiology
Incidence- Often found in the hospital setting, where incidence can be as high as 35%
- Predominant age: elderly
- Predominant 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 carcinoma
- Lymphoma
- Mesothelioma
- Small cell carcinoma of the lung
- Pancreatic carcinoma
- Thymoma
- Pulmonary conditions:
- Asthma/COPD
- Atelectasis
- Cystic fibrosis
- Positive pressure mechanical ventilation
- Pneumonia
- Pulmonary tuberculosis (TB)
- Sarcoidosis
- Neurologic causes:
- Brain tumor
- CNS injury (i.e., subarachnoid hemorrhage, trauma, stroke)
- CNS lupus
- Encephalitis
- Epilepsy
- Guillain-Barré syndrome
- Intracranial surgery
- Meningitis
- Multiple sclerosis
- Other:
- Acute intermittent porphyria
- Delirium tremens
- HIV infection/AIDS
- Rocky Mountain spotted fever
- Idiopathic
Genetics
- 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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Basics
Description
- 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 central nervous system (CNS) disease
- Synonym(s): syndrome of inappropriate secretion of ADH; syndrome of inappropriate antidiuresis
Epidemiology
Incidence- Often found in the hospital setting, where incidence can be as high as 35%
- Predominant age: elderly
- Predominant 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 carcinoma
- Lymphoma
- Mesothelioma
- Small cell carcinoma of the lung
- Pancreatic carcinoma
- Thymoma
- Pulmonary conditions:
- Asthma/COPD
- Atelectasis
- Cystic fibrosis
- Positive pressure mechanical ventilation
- Pneumonia
- Pulmonary tuberculosis (TB)
- Sarcoidosis
- Neurologic causes:
- Brain tumor
- CNS injury (i.e., subarachnoid hemorrhage, trauma, stroke)
- CNS lupus
- Encephalitis
- Epilepsy
- Guillain-Barré syndrome
- Intracranial surgery
- Meningitis
- Multiple sclerosis
- Other:
- Acute intermittent porphyria
- Delirium tremens
- HIV infection/AIDS
- Rocky Mountain spotted fever
- Idiopathic
Genetics
- 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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