This so-called “delayed postoperative hyponatremia” is thought to arise due to the slow and delayed release of ADH stored within the magnocellular osmoregulatory neurons of the posterior lobe of the pituitary gland prior to the injury event [21,35,64,65], a theory bolstered in part by the experimental finding that this delayed hyponatremia can be avoided by preemptive removal of the neurohypophysis in canines [64]. Here, AVP is linked to Hyponatremia.