FRI473 Central Hypothyroidism Following Neonatal Graves Presentation

Disclosure: E. Metzinger: None. K. Halpin: None. Background: Neonatal Graves’ disease is a rare disorder of neonatal autoimmune hyperthyroidism secondary to the transplacental passage of thyroid-stimulating hormone receptor antibodies. Although neonatal Graves’ disease is transient, it is associated with cardiac dysfunction, intrauterine growth restriction, prematurity, craniosynostosis, and developmental delay and can be life-threatening. Additionally, infants with neonatal Graves’ disease can rarely present with primary or central hypothyroidism later in infancy or childhood. This is suspected to be due to the disruption in the hypothalamic-pituitary-thyroid axis or development of the thyroid gland. Clinical Case: Here we describe a case of neonatal Graves’ disease that has been complicated by persistent central hypothyroidism requiring levothyroxine treatment. This was a preterm infant with tachycardia, biventricular heart failure, and hepatomegaly who was transferred to a higher level of care NICU for cardiac and respiratory failure. Pregnancy was complicated by history of maternal Graves’ disease status post radioiodine ablation. Maternal TRAB and thyroid levels were unavailable. Initial thyroid studies on DOL 1 were notable for suppressed TSH of <0.02mcIU/mL, elevated free T4 6.9ng/dL, and elevated total T4 >24.9mcg/dL. Total T3 was normal at 161ng/dL (50-452ng/dL) on DOL 2, and TSI was elevated at 4.8 (TSI Index, normal </= 1.3) on DOL 3. For neonatal thyrotoxicosis, the infant was treated with methimazole, potassium iodide (KI), propranolol, and hydrocortisone. Hydrocortisone was discontinued as the infant clinically improved, and KI was discontinued after 1 week. TFTs were closely followed during admission and methimazole dosing was adjusted as needed. He was discharged from the NICU on DOL 19 on methimazole and propranolol with close outpatient lab monitoring and follow-up. Propranolol was discontinued by 1.5 months of life, and methimazole was discontinued by 2 months of life as TFTs normalized. TSI was negative by four months of life. TSH remained low with decreasing free T4 levels. Ultimately, he was started on levothyroxine at 8.5mcg/kg/day at 2.5 months of age for central hypothyroidism. At that time, TSH was 0.06mcICU/mL and FT4 was 0.7ng/dL. TSH remained low through the first 14 months of treatment with normal free T4 levels on levothyroxine. He has been continued on levothyroxine (average 20mcg/day). Conclusion: This case highlights the severity of neonatal Graves’ disease and the possibility of the subsequent development and persistence of central hypothyroidism following neonatal Graves’ diagnosis despite the resolution of hyperthyroidism and normalization of TSI antibody. Due to the risk of the development of hypothyroidism, it may be worthwhile to continue to trend TSH and FT4 to ensure that the infant has not developed hypothyroidism. Presentation: Friday, June 16, 2023