[Syndrome of inappropriate secretion of antidiuretic hormone]

Hyponatremia is a commonly encountered electrolyte abnormality in clinical practice and in some groups of patients is associated with significant morbidity and mortality. Although the pathophysiology of this disturbance is complex, its understanding is vital to the disorder's evaluation and treatment. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the commonest form of euvolemic hyponatremia and is the clinical and biochemical manifestation of a wide range of disease processes, mostly associated with malignancy, pulmonary, or neurologic disorders, and of pharmacotherapy. Symptoms vary depending on the severity of hyponatremia and, if occur, can range from weakness, mild headache, muscle cramps, nausea, and vomiting to convulsions, coma, and death. Identifying the underlying disorder remains an integral part of the diagnostic evaluation of patients. The most frequently used treatment options include water restriction, oral intake of salt, hypertonic saline and vaptans, being nonpeptide vasopressin antagonists interfering with the antidiuretic effect of the hormone. The aim of our paper is to present a practical diagnostic approach and management of SIADH, with a particular emphasis on the results of recent studies.