No Association Between Transient Hypothyroxinemia of Prematurity and Neurodevelopmental Outcome in Young Adulthood

Context: Transient hypothyroxinemia of prematurity (THoP) has been associated with neurodevelopmental impairment in infancy and childhood. It is not known whether these relations persist into adulthood. Objective: The objective was to examine whether there is an effect of THoP on intelligence quotient (IQ) score and motor functioning at a young adult age. Design: This study was part of the 19-year follow-up of the Project On Preterm and Small-for-ngestational-age birth (POPS) cohort, which included infants born very preterm (ie, <32 wk) and/or with a very low birth weight (ie, <1500 g). Setting: This was a multicenter study. Patients: There were 398 19-year-old participants of the POPS cohort, of whom 120 had THoP. Exposure: T-4 concentrations were obtained through the national neonatal screening program for congenital hypothyroidism. THoP was defined as a total T-4 concentration < - 3 SD of the daily mean (approximately 60 nmol/L). Main Outcome Measures: Main outcome measures were IQ and motor functioning, measured with the digital Multicultural Capacities Test-Intermediate Level and a revised version of Touwen's examination of minor neurological dysfunction, respectively. Results: THoP was not associated with IQ score (mean difference, 0 [95% confidence interval, -3.8 to 3.8] points) or motor function (mean difference, 0.6 [95% confidence interval, -1.3 to 2.5] points) after adjustment for demographic and perinatal characteristics. Conclusions: No associations between THoP and neurodevelopmental outcome at age 19 years were found.