Why post hypophysectomy via transphenoifal approach nurse should check urine specific gravity every 4 hrs?

Diabetes insipidus: After a transphenoidal surgery, you can have a disruption of the production of a pituitary hormone called vasopressin, which normally controls the amount of water that is filtered through the kidneys into your urine. This can result in losing too much water in your urine, a condition called "diabetes insipidus", resulting in diluted urine which can be measured by checking the specific gravity.