Syndrome of inappropriate antidiuretic hormone secretion: Revisiting a classical endocrine disorder

Hyponatremia occurs in about 30% of hospitalized patients and syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. SIADH should be differentiated from other causes of hyponatremia like diuretic therapy, hypothyroidism and hypocortisolism. Where possible, all attempts should be made to identify and rectify the cause of SIADH. The main problem in SIADH is fluid excess, and hyponatremia is dilutional in nature. Fluid restriction is the main stay in the treatment of SIADH; however, cerebral salt wasting should be excluded in the clinical setting of brain surgeries, subarachnoid hemorrhage, etc. Fluid restriction in cerebral salt wasting can be hazardous. Sodium correction in chronic hyponatremia (onset >48 hours) should be done slowly to avoid deleterious effects in brain.