The role of surgery in reversing established hypopituitarism in these patients is not clear, with one meta-analysis reporting only one third of patients with an improvement in pituitary function following tumor resection, with a 4.9- and 2.5-fold risk of developing new anterior pituitary dysfunction and permanent central arginine vasopressin (AVP)-deficiency, respectively, following the surgery [24]. This evidence concerns the gene AVP and hypopituitarism.