ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 64 012 | DOI: 10.1530/endoabs.64.012

Evolution of circulating thyroid hormone levels in preterm infants during the first week of life: Perinatal influences and impact on neurodevelopment

Eerdekens An1, Naulaers Gunnar1, Ortibus Els2, Verhaeghe Johan3, Langouche Lies4 & Vanhole Christine1

1Department of Neonatology, University Hospitals Leuven, KU Leuven, Belgium; 2Department of Development and Regeneration, KU Leuven, Belgium; 3Department of Obstetrics & Gynecology, University Hospitals Leuven, KU Leuven, Belgium; 4Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, KU Leuven, Belgium.

Aim: For several decades, transient hypothyroxinemia of prematurity is topic of debate. The pathophysiology is incompletely understood and consensus on the therapeutic approach is lacking. This study aimed to obtain more insight in the pathogenesis by studying trends in thyroid hormone levels during the first week of life.

Methods: This single-center prospective observational study studied plasma levels of total and free T4, total T3, TSH and TBG in cord blood and at the end of the first week of life in 120 preterm infants (gestational age < 37 weeks). The change over time was calculated (delta, Δ). The impact of perinatal and subsequently postnatal variables on Δwas studied by hierarchical multiple regression. The impact of Δ on the neurodevelopmental outcome at the corrected age of 9 and 24 months, measured by the Bayley Scale of Infants Development II, was assessed by logistic regression.

Main results: Δ(f)T4 levels were negatively affected by gestational age and use of dopamine, whereas only gestational age was associated with low ΔT3 levels. Negative Δ(f)T4 levels were present in 75% of the extremely-low-for gestational-age infants, whereas 23·5% had a negative Δ T3 level. There was an increased risk for an abnormal mental developmental score (<85) with decreasing ΔT3 at 9 months, corrected age, but not at 24 months.

Conclusions: A negative evolution in circulating thyroid hormone levels is principally an immaturity phenomenon, whereas dopamine can further suppress the hypothalamic-pituitary-thyroid axis. There is at least a temporary negative effect of this evolution on the infants’ neurodevelopment.

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