title: Serum free T4 and thyroid stimulating hormone levels in preterm infants and relationship between these levels and respiratory distress syndrome.
abstract: BACKGROUND
  There have been few studies of the thyroid stimulating hormone (TSH) surge in extremely low-birthweight (ELBW) infants, and the relationship between thyroid hormones and respiratory distress syndrome (RDS) has yet to be clarified. The present study sought to determine the serum levels of free T4 (fT4) and TSH in ELBW infants and to examine the relationship between these levels and the development of RDS.
  
  
  METHODS
  The authors measured serum fT4 and TSH levels soon after birth in 449 preterm infants, who were born at 22-36 weeks of gestation, and determined the associations between these levels, the incidence of RDS, and the recognized clinical factors associated with RDS.
  
  
  RESULTS
  Serum fT4 and TSH levels, and the fT4/TSH ratio, in the group at 22-24 weeks of gestation were significantly lower than those in the group at 28-36 weeks. The levels and ratio increased significantly with increasing gestational age. There were significant correlations between the serum fT4 level and the birthweight, Apgar score, and gender, and between the serum TSH level and the gestational age, mode of delivery, and birthweight. No significant relationship between the incidence of RDS and the serum levels of fT4 and TSH was observed.
  
  
  CONCLUSIONS
  The authors' results suggest that the serum levels of fT4 and TSH in ELBW infants are very low, and that these levels are not correlated with the occurrence of RDS.
authors.affiliation: Department of Pediatrics, Juntendo University School of Medicine, Tokyo, Japan. ktanaka@med.juntendo.ac.jp
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Shimizu
authors.forename: Atsuto
authors.initials: A
authors.lastname: Hosaka
authors.forename: Akifumi
authors.initials: A
authors.lastname: Tokita
authors.forename: Seigo
authors.initials: S
authors.lastname: Shiga
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Yamashiro
mesh_terms: D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood*; D008297:Male; D012127:Respiratory Distress Syndrome, Newborn / Q000097:blood*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*
chemical_list: D013972:Thyrotropin; D013974:Thyroxine