201 - Transient Hypothyroxinemia and Growth Velocity in Preterm Infants
Saturday, April 29, 2023
3:30 PM – 6:00 PM ET
Poster Number: 201 Publication Number: 201.214
Meira S. Zibitt, Medical College of Georgia at Augusta University, Augusta, GA, United States; Steven Herrmann, Children's Hospital of Georgia, Augusta, GA, United States; Cynthia A. Mundy, Children's Hospital of Georgia, Augusta, GA, United States; Brian Stansfield, Medical College of Georgia at Augusta University, Augusta, GA, United States
Medical Student Medical College of Georgia at Augusta University Augusta, Georgia, United States
Background: Transient hypothyroxinemia is common in preterm infants and is characterized by low free thyroid hormone (FT4) associated with low or normal thyroid stimulating hormone (TSH). Transient hypothyroxinemia of prematurity (THOP) may be associated with poor cognitive outcomes in school-age children. Reported reference ranges for FT4 and TSH increase with advancing gestational age; however, thresholds for FT4 and TSH to diagnose transient hypothyroxinemia of prematurity (THOP) have not been established. Further, links between THOP and intermediate outcomes such as growth have not been investigated previously. Objective: The purpose of this study was to establish relationships between FT4 and TSH and age, measured by day of life (DOL) and post-menstrual age (PMA), in preterm infants less than 32 weeks PMA. We also sought to identify potential associations between THOP and intermediate growth outcomes in preterm infants. Design/Methods: Preterm neonates < 32 weeks PMA admitted to the regional neonatal intensive care unit (NICU) at the Children’s Hospital of Georgia between January 2010 and July 2022 were eligible for study inclusion. FT4 and TSH values were obtained on 621 eligible neonates between DOL 4 and 14. Growth velocity (g/kg/day) from DOL 14 to DOL 28 and 36 weeks PMA were calculated for each neonate and potential explanatory variables (PMA, sex, and race) were incorporated into multivariate regression models to identify associations between THOP and growth velocity. Results: PMA, but not DOL, showed a positive correlation with both FT4 (R2 = 0.2, P < 0.001) and TSH (R2 = 0.1, P = 0.01) values in the first 2 weeks of life (n = 621). Additionally, weak but statistically significant associations between FT4 and growth velocity at DOL 28 (n = 565) and 36 weeks PMA (n = 550) were identified (Figures 1 and 2). Finally, preterm infants with EGA-adjusted FT4 below the 5th percentile exhibited modestly lower growth velocity at 36 weeks PMA than infants with FT4 ³ 5th percentile (14.2 vs. 14.9 g/kg/day, P = 0.02, Figure 3). No difference in growth velocity at DOL 28 was observed.
Conclusion(s): This study identifies weak linear correlations between FT4 and growth velocity at DOL 28 and 36 weeks PMA. Additionally, low EGA-adjusted FT4 is associated with modestly lower growth velocity at 36 weeks PMA. These data suggest that THOP may affect weight growth velocity in preterm infants.
