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Low thyroxinaemia occurs in the majority of very preterm newborns

  • Neonatology
  • Published:
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Abstract

Transient hypothyroxinaemia with normal thyroid stimulating hormone (TSH) levels is a well-known condition in preterm neonates and is generally assumed to be a harmless epiphenomenon of prematurity. This assumption is, however, based on studies that included very few neonates with a gestational age (GA) below 30 weeks. We therefore measured serum free thyroxine (FT4) and serum TSH on days 1 and 14 in 263 neonates with a GA between 26 and 41 weeks. In 13 infants (5%), transient hypothyroidism (low FT4 and TSH>20 mU/l on day 14) was found. In the remaining 250 patients FT4 on days 1 and 14 but not TSH correlated positively with GA. In neonates with a GA of 35–41 weeks, FT4 increased postnatally to levels within or above the normal adult range. In contrast, in the very preterm group (26–31 weeks) the already low FT4 levels declined to values significantly below the range observed in term neonates. A significant proportion of these neonates had FT4 levels within the hypothyroid range. There was no difference in thyroid function between neonates treated with povidone-iodine or chlorhexidine.

Conclusion

Very preterm neonates have FT4 levels on day 14 that are much lower than is generally assumed while TSH remains in the normal range. We therefore propose to measure FT4 in all preterms with a GA below 33 weeks, during the 2nd week of life.

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Abbreviations

GA :

gestational age

FT 4 :

free thyroxine

NICU :

neonatal intensive care unit

TBG :

thyroxine binding globulin

TRH :

thyrotropin releasing hormone

TSH :

thyroid stimulating hormone

TT 4 :

total thyroxine

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Authors and Affiliations

  1. Department of Paediatrics, Antwerp University Hospital, Wilrijkstraat 10, B-2650, Antwerp, Belgium

    R. P. Rooman, M. V. L. Du Caju, L. Op De Beeck, M. Docx, P. Van Reempts & K. J. Van Acker

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  1. R. P. Rooman
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  2. M. V. L. Du Caju
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  3. L. Op De Beeck
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  4. M. Docx
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  5. P. Van Reempts
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  6. K. J. Van Acker
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Rooman, R.P., Du Caju, M.V.L., Op De Beeck, L. et al. Low thyroxinaemia occurs in the majority of very preterm newborns. Eur J Pediatr 155, 211–215 (1996). https://doi.org/10.1007/BF01953940

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  • DOI: https://doi.org/10.1007/BF01953940

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