title: Thyroid function in healthy Thai neonates.
abstract: OBJECTIVE
  To construct a normative data for serum thyroxine (T4), free T4 (FT4), triiodothyronine (T3) and thyrotropin (TSH) in Thai neonates.
  
  
  METHODS
  A cross-sectional study of 275 healthy full-term neonates was conducted. Blood samples were obtained from umbilical cords of the neonates and from heel pads of infants aged 1-30 days. Hormone measurements included serum T4, FT4, T3 and TSH.
  
  
  RESULTS
  Mean serum T4 and FT4 levels rapidly increased after delivery to the maximum level at 1-3 days of age. Thereafter, they declined to a steady state level within 2-4 weeks. Mean serum T3 level was very low at birth. The concentration increased 3-5 times and reached a steady state levels within 1 week. In contrast, mean serum TSH declined from birth and the level at 1-3 days of age was slightly less than that of the cord blood. It changed little after 3 days of age. Previous studies have shown a transient TSH surge in the first 24-48 hour of life. TSH surge was not apparent in our study because samples were not obtained from infants < 24 hours old. Therefore, if TSH is measured for screening of congenital hypothyroidism, samples should be obtained from umbilical cord or infants aged > 48 hours.
  
  
  CONCLUSIONS
  This study provides the normative data for thyroid function tests in Thai full-term neonates. These data are useful for detection and verification of hypothyroidism in a screening program for congenital hypothyroidism.
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: P
authors.initials: P
authors.lastname: Mahachoklertwattana
authors.forename: A
authors.initials: A
authors.lastname: Sriphrapradang
authors.forename: S
authors.initials: S
authors.lastname: Supapannachart
authors.forename: A
authors.initials: A
authors.lastname: Pongsuwan
authors.forename: L
authors.initials: L
authors.lastname: Choubtum
authors.forename: R
authors.initials: R
authors.lastname: Rajatanavin
mesh_terms: D003430:Cross-Sectional Studies; D006801:Humans; D007231:Infant, Newborn / Q000502:physiology*; D012016:Reference Values; D013785:Thailand; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine