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Thyroid function and dysfunction in premature infants

Delbert A Fisher1

  • 1David Geffen School of Medicine at UCLA, Harbor UCLA Medical Center, Torrance, CA 90509, USA. fisherd1@cox.net

Pediatric Endocrinology Reviews : PER
|July 24, 2007
PubMed

Insights

Advances in premature infant care have increased survival rates for very low birth weight (VLBW) infants. However, these infants often experience transient hypothyroxinemia of prematurity (THOP), impacting neurological development, with supplementation trials yielding inconclusive results.

Area of Science:

  • Neonatology
  • Endocrinology
  • Perinatal Medicine

Background:

  • Significant advances in neonatal care have reduced mortality in premature infants, particularly very low birth weight (VLBW) infants.
  • Increased survival of extremely preterm infants (<24 weeks gestation) leads to a larger population requiring intensive care.
  • VLBW infants exhibit unique thyroid function patterns, including transient central hypothyroidism and non-thyroidal illness (NTI) syndrome.

Purpose of the Study:

  • To investigate the roles of thyroid system immaturity and NTI in transient hypothyroxinemia of prematurity (THOP).
  • To clarify the impact of THOP on subsequent neurological deficits in VLBW infants.
  • To evaluate the effectiveness of thyroxine supplementation in VLBW infants.

Main Methods:

  • Observational studies analyzing thyroid hormone levels (TSH, T4, T3, free T4, reverse T3, TBG) in VLBW infants.
  • Review of existing thyroxine supplementation trials.
  • Planned and ongoing research studies.

Main Results:

  • VLBW infants show decreased TSH and T4 responses to parturition, with low total T4 and TSH, and variable free T4 in early postnatal weeks.
  • A high prevalence of morbidity is observed, often correlating with reduced thyroid hormone levels, mimicking NTI.
  • Previous thyroxine supplementation trials have produced inconclusive results regarding benefits.

Conclusions:

  • The etiologies of THOP and its impact on neurological outcomes in VLBW infants require further elucidation.
  • The precise role of thyroid system immaturity versus NTI in THOP remains unclear.
  • Further research, including ongoing trials, is necessary to determine optimal management and potential benefits of thyroxine supplementation.

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