7593 Early re-evaluation using levothyroxine dose requirements in infancy in patients with congenital hypothyroidism

Abstract Disclosure: M. Yoo: None. E. Joo: None. S. Kim: None. J. Lee: None. Background: Congenital hypothyroidism (CH) is the most common endocrine disorder in the neonatal period. CH can lead to permanent mental retardation if left untreated. The prevalence of CH has recently increased due to neonatal screening programs for CH. Congenital Hypothyroidism: The 2020-2021 Consensus Guidelines Update, recently published in the Endo-European Reference Network (Endo-ERN), suggested that a reevaluation of early treatment withdrawal after 6 months could be performed in patients with CH. In Korea, there has been no study on early reevaluation after 6 months, so we conducted this study. Methods: As a retrospective study, patients diagnosed with CH from January 2013 to December 2022 at the Department of Pediatrics, Inha University evaluated thyroid function tests (TFT) at the time of diagnosis and LT4 dose and body weight during treatment. Results: A total of 105 patients were diagnosed with CH, 64 were classified as transient CH (TCH) and 41 as permanent CH (PCH). Patients younger than 2 years who did not complete the reevaluation were excluded. At diagnosis, thyroid stimulating hormone (TSH) levels were higher in the PCH group than in the TCH group (47.8 ± 58.0 mIU/L vs 69.2 ± 94.1 mIU/L, respectively). At 6 months, 1 and 2 years, the mean dose of levothyroxine (μg/kg/day) was significantly lower in the TCH group than in the PCH group. (3.34 ± 0.94 vs 3.63 ± 1.03 μg/kg/day, p<0.05, 2.56 ± 0.95 vs 3.16 ± 1.14 μg/kg/day, p<0.01 and 2.07 ± 0.57 vs 3.01 ± 1.14 μg/kg/day, p<0.01). Based on the Receiver Operating Characteristic (ROC) curve, the optimal cutoff doses of LT4 for prediction of TCH at 6 month was 3.24 µg/kg/day (area under the curve=0.643; 95% CI, 0.529-0.757; sensitivity, 58.6%; specificity, 70.3%) Conclusion: Early re-evaluation after 6 month for withdrawal of LT4 treatment is possible in patients with CH if the patient has gland in situ, no family history, and low LT4 dose requirements. Presentation: 6/1/2024