Causes of SIADH can be divided into the following categories:
- Nervous system disorders – Head trauma, meningitis, encephalitis, subdural hematoma, subarachnoid hemorrhage, Guillain-Barre syndrome, multiple sclerosis, amyotrophic lateral sclerosis, ventriculoperitoneal shunt occlusion, Shy-Drager syndrome, and cerebrovascular accident.
- Neoplasia – Small cell lung cancer, non-small cell lung cancer, mesothelioma, bronchial adenoma, primary brain tumors, thymoma, Ewing sarcoma, non-Hodgkin lymphoma, stomach cancer, neuroendocrine carcinomas, duodenal cancer, pancreatic cancer, bladder cancer, and uterine cancer.
- Pulmonary diseases – Chronic obstructive pulmonary disease, cystic fibrosis, pneumonia, asthma, pneumothorax, acute respiratory failure requiring mechanical ventilation, pulmonary aspergillosis, pulmonary fibrosis, tuberculosis, and sarcoidosis.
- Drug-induced SIADH – Chemotherapeutic agents including cyclophosphamide, ifosfamide, vincristine, vinblastine, cisplatin, melphalan, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, ciprofloxacin, griseofulvin, carbamazepine, chlorpropamide, high-dose oxytocin, and vasopressin or desmopressin.
Presenting symptoms relate to the rapidity of development of hyponatremia. Patients with slowly progressive hyponatremia are often asymptomatic, while those with rapid development of hyponatremia may present with headache, confusion, anorexia, malaise, or even seizures and coma. Physical examination often reveals a normotensive and euvolemic patient.