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-gestational-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: T4 concentrations were obtained through the national neonatal screening program for congenital hypothyroidism. THoP was defined as a total T4 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.