Document Detail


Reference ranges for thyroid function tests in premature infants beyond the first week of life.
MedLine Citation:
PMID:  11774014     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVES: To establish reference ranges for the more sensitive assays of thyrotropin and the best available assays of free thyroxine in premature infants after the first week of life. STUDY DESIGN: Free thyroxine measurements by direct equilibrium dialysis and thyrotropin measurements by third generation immunometric assay were measured in 120 healthy premature infants 25 to 36 weeks' gestation at birth and every 3 weeks until hospital discharge. Infants were stratified by postconceptional age. Differences in free thyroxine and thyrotropin levels among groups were determined by ANOVA. Correlations between hormone measurements and gestational and postnatal ages were sought by linear regression analysis. Reference ranges were determined as arithmetic (free thyroxine) and geometric (thyrotropin) mean+/-2 SD ranges. RESULTS: From 120 infants, 164 samples were obtained and grouped by postconceptional age at sampling. Free thyroxine was not different among postconceptional age groups and did not correlate with gestational or postnatal age. The free thyroxine reference range based on these data was 10 to 33 pmol/l (0.8 to 2.6 ng/dl). Thyrotropin did not correlate with gestational age. There was a clinically trivial but statistically significant (r(2)=0.03, p<0.05) correlation of thyrotropin with postnatal age. The thyrotropin reference based on these data was 0.8 to 12 mU/l. CONCLUSIONS: Free thyroxine was closely regulated in these premature infants and levels were similar to those in older children and adults, once the natal surge in thyrotropin has subsided. After the first week of life a single range for each hormone appeared appropriate for all premature infants until 40 weeks postconceptional age.
Authors:
S J Clark; D D Deming; J R Emery; L M Adams; E I Carlton; J C Nelson
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of perinatology : official journal of the California Perinatal Association     Volume:  21     ISSN:  0743-8346     ISO Abbreviation:  J Perinatol     Publication Date:  2001 Dec 
Date Detail:
Created Date:  2002-01-04     Completed Date:  2002-03-01     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  8501884     Medline TA:  J Perinatol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  531-6     Citation Subset:  IM    
Affiliation:
Department of Pediatrics, Loma Linda University School of Medicine, Coleman Pavilion, Loma Linda, CA 92354, USA.
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MeSH Terms
Descriptor/Qualifier:
Female
Humans
Infant, Newborn
Infant, Premature / physiology*
Male
Prospective Studies
Reference Values
Thyroid Function Tests*
Thyrotropin / blood*
Thyroxine / blood*
Chemical
Reg. No./Substance:
7488-70-2/Thyroxine; 9002-71-5/Thyrotropin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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