Serum free thyroxine values in term, premature, and sick infants

Darrell M. Wilson, Andrew O. Hopper, I. Ross McDougall, Monika F. Bayer, Raymond L. Hintz, David K. Stevenson, Ron G. Rosenfeld

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Free thyroxine concentrations were determined by radioimmunoassay in 96 infants within an intensive care nursery and in 32 healthy term infants. Sera for free T4 levels were drawn simultaneously with the filter paper specimens for T4 obtained to screen these infants for congenital hypothyroidism. The mean free T4 level in 20 adults was 1.38±0.03 ng/dl (mean±SEM). The mean in the ICN infants was 3.48±0.18 ng/dl and in healthy term infants, 4.24±0.23 ng/dl. Like T4, free T4 correlated positively with increasing gestational age and birth weight, and was lower in infants with RDS. Although 66% of the ICN infants had T4 levels below the statistically selected screening level (fifth percentile), all of these infants had free T4 levels greater than 0.8 ng/dl. Two additional infants with untreated congenital hypothyroidism had free T4 levels of 0.3 and 0.4 ng/dl. The measurement of free T4 appears to be an accurate indicator of thyroid function in these infants.

Original languageEnglish (US)
Pages (from-to)113-117
Number of pages5
JournalThe Journal of pediatrics
Issue number1
StatePublished - Jul 1982
Externally publishedYes

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


Dive into the research topics of 'Serum free thyroxine values in term, premature, and sick infants'. Together they form a unique fingerprint.

Cite this