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Developmental trends in cord and postpartum serum thyroid hormones in preterm infants

Fiona L R Williams1, Judith Simpson, Caroline Delahunty

  • 1Community Health Sciences, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, United Kingdom.

The Journal of Clinical Endocrinology and Metabolism
|November 9, 2004
PubMed

Insights

Thyroid hormone levels in preterm infants show distinct postnatal trends. Extremely preterm infants (23-27 weeks) exhibit reversed T4 trends, indicating hypothyroidism.

Area of Science:

  • Neonatal endocrinology
  • Pediatric thyroidology
  • Perinatal medicine

Background:

  • Thyroid hormone levels undergo significant changes during the transition from fetal to neonatal life.
  • Preterm infants, especially those born extremely early, may experience altered thyroid hormone dynamics due to physiological immaturity.

Purpose of the Study:

  • To delineate postnatal thyroid hormone (T4, FT4, TSH, T3, rT3, T4 sulfate) trends in preterm infants across different gestational ages (23-34 weeks).
  • To compare these trends with those observed in term infants and cord blood levels.

Main Methods:

  • Longitudinal study measuring serum thyroid hormone levels at birth and on days 7, 14, and 28 in preterm infants (n=540) and term infants (n=812).
  • Gestational age groups for preterm infants: 23-27, 28-30, and 31-34 weeks.

Main Results:

  • Preterm infants showed variable postnatal changes in TSH, rT3, T4-binding globulin, T3, and T4 sulfate compared to cord levels.
  • Term infants presented with hyperthyroxinemia relative to cord and adult levels.
  • Postnatal T4 increases were blunted or reversed in preterm infants, with the 23-27 week group showing significant hypothyroxinemia.

Conclusions:

  • The 23-27 week gestational age group exhibits unique hypothyroxinemia, despite FT4 levels being within the expected range for their gestational age.
  • Thyroid hormone regulation is significantly impacted by gestational immaturity, necessitating careful monitoring in extremely preterm neonates.

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