Posterior pituitary (PP) evaluation in patients with anterior pituitary defect associated with ectopic PP and septo-optic dysplasia

Objective: Controversies exist about posterior pituitary (PP) function in subjects with ectopic PP (EPP) and with cerebral midline defects and/or their co-occurrence. We investigate water and electrolyte disturbances in patients at risk for PP dysfunction. Design: The study was conducted in a single Pediatric Endocrinology Research Unit. Methods: Forty-two subjects with childhood-onset GH deficiency were subdivided into five groups: normal magnetic resonance imaging (n = 8, group 1); EPP (n = 15, group 2); septo-optic dysplasia (SOD) with normal PP (n = 4, group 3); EPP and SOD without (n = 7, group 4), and with additional midline brain abnormalities (n = 8, group 5). At a mean age of 16.0 +/- 1.1 years, they underwent a 120 min i.v. infusion with hypertonic 5% saline and evaluation of plasma osmolality (Posm), arginine vasopressin (AVP), thirst score (in groups 1 and 2), and urinary osmolality were performed. Results: Mean Posm and AVP significantly increased from baseline scores (284.7 +/- 4.9 mosm/kg and 0.6 +/- 0.2 pmol/l) to 120 min after saline infusion (300.5 +/- 8.0 mosm/kg and 10.3 +/- 3.3 pmol/l, P < 0.0001). Group 5 showed higher mean Posm and lower mean AVP at all time points (P < 0.0001). Mean thirst score did not show a significantly different trend between the groups 1 and 2. Urine osmolality was above 750 mosm/kg in all but seven patients after osmotic challenge. Conclusions: Patients with midline brain abnormalities and EPP have defective osmoregulated AVP. Patients with EPP and congenital hypopituitarism have normal PP function.