SUN-192 Neonatal Diagnosis of Pituitary Stalk Interruption Syndrome

Abstract Disclosure: T. Handa: None. R. Soohey: None. M. Gortakowski: None. Introduction: Pituitary stalk interruption syndrome (PSIS) is a congenital pituitary disorder characterized by MRI findings a thin or interrupted pituitary stalk, ectopic posterior pituitary tissue, and hypoplasia or aplasia of the anterior pituitary. PSIS commonly presents with combined pituitary hormone deficiencies at a variable age of onset. Presentation: A female infant with an uncomplicated prenatal course born at 39 5/7 weeks was admitted to the NICU for apnea and desaturation with concern for seizure after admission. Initial point of care glucose was less than 20mg/dL. MRI/MRA ruled out venous sinus thrombosis and hypoxic-ischemic encephalopathy (HIE) but did not comment on pituitary abnormalities. Critical sample at 6 hours of life (HOL) showed serum glucose 38 mg/dL (50-80 mg/dL), insulin 2.9 uU/mL (2.6-24.9), beta-hydroxybutyrate less than 0.05 mmol/L (0.27-5.0), and cortisol 0.9 mcg/dL. Given lab values, MRI was requested to be re-read with attention to the pituitary. A hyperintense focus at the inferior margin of the pituitary infundibulum compatible with an ectopic posterior pituitary was found, consistent with PSIS. Hypoglycemia was treated with IV Dextrose up to a glucose infusion rate of 10mg/kg/min, and the infant was weaned off dextrose-containing fluids by DOL 14. On DOL 4, an ACTH stimulation test was consistent with central adrenal insufficiency (CAI) (baseline cortisol 0.6 mcg/dL, ACTH 3.3 pg/mL (7.2-63.3) and cortisol 60 minutes 5.9 mcg/dl). Stress-dose hydrocortisone was started and infant transitioned to maintenance with clinical improvement. Levothyroxine was further started for Serial low-normal free T4 values for age with normal TSH, suggestive of central hypothyroidism (CeH). At outpatient follow up at approximately 6 weeks of age, IGF-1 was 12 ng/mL (17-185), and IGFBP-3 was 351 mcg/L (1053-3271). Infant was subsequently started on somatotropin therapy for growth hormone deficiency (GHD). Discussion: This case highlights the variable presentation of PSIS. PSIS is a rare diagnosis in the neonatal period, with prevalence rates not well documented. In this patient, an MRI was obtained to evaluate for HIE however revealed findings consistent PSIS. Further, given an inappropriate elevation of insulin in the setting of hypoglycemia this was suggestive of transient stress hyperinsulinism. CAI and CeH were identified and treated in the NICU and GH therapy was started in the outpatient setting for GHD. This case emphasizes the importance of evaluating for combined hormone deficiencies in patients with PSIS. Conclusion: We present a unique case of PSIS diagnosed during the initial evaluation for concern for HIE. This case illustrates the diagnostic role of MRI and a complete biochemical evaluation for affected axes. Treatment of PSIS involves hormone supplementation tailored to the patient’s clinical picture. Presentation: Sunday, July 13, 2025