The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by the excessive and inappropriate secretion of antidiuretic hormone (ADH) either by a tumor or as the result of other influences acting on the posterior pituitary gland (see Table).
There is a strong association with small cell carcinoma of the lung and SIADH occurs less commonly with a variety of other tumors. In SIADH there is reduced renal excretion of water, leading to a state of water intoxication with hyponatraemia and hypotonicity of the plasma.
Causes of SIADH
- Tumors: small cell lung cancer, others
- Neurological: primary or metastatic tumor, post neurosurgery
- Pulmonary: pneumonia, abscess, TB
- Drugs: vincristine, cyclophosphamide, carbamazepine, antidepressants (TCAs, SSRIs)
Signs and symptoms
- Gastrointestinal: anorexia, nausea
- Musculoskeletal: muscle aches, generalized muscle weakness, neuromuscular, myoclonus, decreased reflexes, ataxia, tremor, asterixis
- Respiratory: Cheyne-Stokes respiration
- Neurological: dysarthria, lethargy, confusion, delirium, seizures, coma (from brain swelling)
- Electrolyte: euvolemic patients with low serum osmolality, hyponatremia and normal serum creatinine.
See reference for more information. Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. 4th ed., Oxford University Press, 2004. p. 415.
Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on July 14, 2017.