SAT-453 Delayed TSH Elevation in Small for Gestational Age Infants: A Need for Second Screening?

The incidence of CH with a delayed TSH elevation was higher in ELBW and VLBW infants compared with infants weighing ≥1500 grams. Second screening should be considered in preterm neonates, low birth weight (LBW) and very low-birth weight (VLBW) neonates, ill and preterm newborns admitted to NICU, specimen collection within the first 24 hours of life, and multiple births (particularly same-sex twins). Purpose of this study was to determine incidence of delayed TSH elevation with or without congenital hypothyroidism in SGA infants and to Investigate necessity for second screening. Retrospective analysis was performed. 66 SGA newborns with 34-40 weeks’ gestation born at Keimyung University Dongsan Medical Center from 2015 to 2018 were enrolled. Primary screening was performed 48 hours - 7 days after birth. Second screening including venous TSH and venous free T4 at postnatal 8-40 days. Exclusion criteria were infants with congenital hypothyroidism at primary screening (NBS), descendants of mothers with immune thyroid disease, congenital malformations, renal, hepatic, and metabolic diseases, history of steroid or dopamine usage. Initial NBS were collected onto pre-printed filter at the age of 2-7 days by heel prick. (normal TSH < 10 mIU/L). Second sample was obtained at the age of 8-49 days by venous sampling (normal TSH < 5 mIU/L). TSH and free T4 were measured on venous samples with Cobas 8000 e801 (electrochemiluminescence, Roche, Diagnostics, Basel, Switzerland) using standard methods. Incidence of delayed TSH elevation was 27% (18/66). Of them number of transient hyperthyrotropinemia was 13. Mean TSH at initial elevation was 7.56 mIU/L and median age at initial TSH elevation was 18.6 days. Median age at resolution of TSH elevation was 41.5 days. Number of hypothyroidism undergoing l-thyroxine medication was 5. Mean TSH at initial elevation was 22.1 mIU/L. Median age at initial TSH elevation was 14 days. Mean peak TSH was 23.4 mIU/L. The presence of delayed TSH elevation was not related to very low birth weight. SGA infants might be at a risk of delayed TSH elevation. Considering 2(nd) screening test within 1 month. Further study with more SGA infants are needed. Limitation of this study was relative small number of patients and iodine status was not considered