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Antenatal glucocorticoids increase early total thyroxine levels in premature infants

Camilia R Martin1, Linda J Van Marter, Elizabeth N Allred

  • 1Department of Neonatology, Beth Israel Deaconess Medical Center, Division of Newborn Medicine, Boston, MA 02215, USA. cmartin1@bidmc.harvard.edu

Biology of the Neonate
|February 11, 2005
PubMed

Insights

Antenatal glucocorticoids, used to support preterm delivery, were associated with higher early total thyroxine (T4) levels in extremely premature infants. This finding suggests a potential influence on neonatal thyroid function.

Area of Science:

  • Neonatalogy
  • Endocrinology
  • Obstetrics

Background:

  • Hypothyroxinemia in premature infants is linked to severe adverse outcomes, including neurodevelopmental deficits and mortality.
  • Understanding factors influencing thyroid function in preterm neonates is critical.
  • Antenatal glucocorticoid exposure is common in threatened preterm deliveries, but its impact on neonatal thyroid function is understudied.

Purpose of the Study:

  • To investigate the association between antenatal glucocorticoid exposure and early total thyroxine (T4) levels in extremely premature infants.
  • To determine if antenatal glucocorticoids modify neonatal thyroid hormone levels shortly after birth.

Main Methods:

  • A cohort of 521 infants born between 23-28 weeks gestational age was studied across four medical centers.
  • Serum total T4 levels were measured in the first postnatal week, sourced from newborn screening programs.
  • Antenatal glucocorticoid exposure was categorized as none, partial, or complete, with a complete course defined by specific betamethasone or dexamethasone dosing.

Main Results:

  • Infants receiving a complete course of antenatal glucocorticoids exhibited significantly higher total T4 levels (0.8 microg/dl greater) compared to unexposed infants (p = 0.03).
  • This association persisted after controlling for maternal, perinatal, and neonatal confounding factors.
  • The observed increase in T4 levels was statistically significant, indicating a potential biological effect.

Conclusions:

  • Complete antenatal glucocorticoid administration is associated with elevated total thyroxine levels in the first week of life for extremely premature infants.
  • The relationship between antenatal glucocorticoids and neonatal thyroid function is not fully explained by known confounding variables.
  • These findings suggest that antenatal glucocorticoids may directly influence early thyroid hormone regulation in preterm neonates.
Abstract

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