From the Guidelines
Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion is primarily caused by central nervous system disorders, pulmonary disorders, certain medications, and various malignancies that lead to excessive release of antidiuretic hormone (ADH). The causes of SIADH can be multifaceted, involving different systems and conditions.
- Central nervous system disorders such as head trauma, brain tumors, meningitis, encephalitis, and stroke are common causes, as they can disrupt the normal regulation of ADH release 1.
- Pulmonary disorders like pneumonia, tuberculosis, lung abscess, and small cell lung cancer are also frequent culprits, potentially due to the production of ectopic ADH or the stimulation of ADH release.
- Various medications can trigger SIADH, including antidepressants (particularly SSRIs), antipsychotics, anticonvulsants, chemotherapy agents, and opioids, as noted in the context of managing heart failure and hyponatremia 1.
- Certain malignancies, especially small cell lung cancer, pancreatic cancer, and lymphomas, can produce ectopic ADH, leading to SIADH.
- Other causes include HIV infection, acute intermittent porphyria, and major surgery, which can indirectly affect ADH regulation or lead to conditions conducive to SIADH development. The excessive ADH causes increased water reabsorption in the kidneys, leading to dilutional hyponatremia with concentrated urine despite low serum osmolality, a condition that may require careful management, including the consideration of vasopressin antagonists in certain cases, as discussed in the context of heart failure management 1.
From the FDA Drug Label
Hyponatremia — Hyponatremia may occur as a result of treatment with SSRIs and SNRIs, including Prozac. In many cases, this hyponatremia appears to be the result of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) The causes of Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion include treatment with SSRIs and SNRIs, such as Prozac 2.
From the Research
Causes of SIADH
The causes of Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion are varied and can be classified into several categories, including:
- Malignancy 3
- Pulmonary diseases 3, 4
- Central nervous system diseases 3, 4
- Medications, such as:
- Traumatic brain injury (TBI) 6
- Rare activating mutations of the V2 receptor 3
- Other diseases, such as meningo-encephalitis 6
Etiology and Diagnosis
Determining the etiology of SIADH is crucial, as removal of the underlying cause offers the most effective therapy 3, 4. Diagnosis involves a precise evaluation of volemia and the elimination of differential diagnoses 4. A chest radiograph or a chest CT-scan may be necessary in the case of a newly diagnosed SIADH 4.
Treatment and Management
Treatment of SIADH is guided by symptoms and their severity, as well as the level of plasma sodium 3. Fluid restriction is often the first-line treatment for mild or moderate hyponatremia 3, 4. However, etiologic treatment is necessary for the disappearance of SIADH 4. Other treatment options include loop diuretics, salt tablets, urea, and V2 receptor antagonists 3. Demeclocycline can also be used to manage chronic hyponatremia due to SIADH, especially in cases where fluid restriction is challenging 6.