ESPE Abstracts

Background: Preterm newborns are at risk of becoming transiently hypothyroxinaemic, which has been associated with neurodevelopmental impairments in childhood. It is not known whether these associations persist into adulthood.

Objective and hypotheses: We studied the relation between transient hypothyroxinaemia of prematurity and IQ, neuromotor functioning and problem behaviour at young adult age.

Method: This was a prospective study among 473 19-year-old subjects born very preterm (i.e., <32 weeks) and/or with a very low birth weight (i.e., <1,500 g) from the project on preterm and small-for-gestational-age infants (POPS) cohort. Total thyroxine (T₄) concentrations were obtained through the national neonatal screening program for congenital hypothyroidism. Children with congenital hypothyroidism were excluded. We studied whether hypothyroxinaemia, defined as a total T₄ <−3 S.D., was associated with low IQ (<85), measured with the digital Multicultural Capacities Test-Intermediate Level; impaired neuromotor function (<10th percentile), using Touwen’s examination of mild neurologic dysfunction; and behavioral problems, assessed with the Young Adult Self Report and the Young Adult Behavior Checklist for parents.

Results: Hypothyroxinaemia did not influence the risks of low IQ score or impaired motor functioning, as evidenced by an odds ratio of 1.2 (95% CI: 0.5–2.5) and 0.7 (95% CI: 0.4–1.2) respectively after adjusting for perinatal and family background variables. Hypothyroxinaemia was associated with a 2.0 (95% CI: 1.1–3.7) – fold increased risk of parent-reported total problem behavior after correction for perinatal and family background variables. No associations were found for other parent-reported or self-reported problems.

Conclusion: No associations between transient hypothyroxinaemia of prematurity and neurodevelopment or behavioural problems at the age of 19 years were found, except for parent-reported total problem behaviour. Therefore, this study adds to the evidence not to routinely screen for hypothyroxinaemia in preterm newborns.