The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) (Bartter and Schwartz, 1967) is defined as low effective plasma osmolality due to impaired renal water dilution together with impaired thirst center regulation once effective hypovolemia and corticotropin deficiency are ruled out (Robertson, 2006).

Impaired water dilution is encountered following stimulation of voloreceptors triggering ADH (i.e., vasopressin) secretion through brain circumventricular organ stimulation [including notably the subfornical organ (SFO)] (Bichet, 2019). This condition is reversed as soon as volemia is restored: hyponatremia is corrected within hours, unlike withdrawal of drugs inducing SIADH, in which optimal water dilution recovery usually takes several days or weeks. Therefore, diuretics will be beyond the scope of this review.