AVP and inappropriate ADH syndrome: Delayed postoperative hyponatremia (DPH), a common cause of unplanned readmission after transsphenoidal surgery (TSS) for pituitary adenoma, is primarily attributed to the syndrome of inappropriate antidiuretic hormone secretion (SIADH), often triggered by surgical manipulation of the pituitary stalk (Klaassen et al., 2025; Bernardi et al., 2023; Snyder et al., 2022; Blair et al., 2017).