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:Theobjectivewastoexaminewhetherthere isaneffect ofTHoPonintelligence 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-forgestational-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.THoPwasdefined as a total T₄ concentration <-3 SDof the dailymean (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.