Document Detail

Early Pregnancy Reference Intervals of Thyroid Hormone Concentrations in a Thyroid Antibody-Negative Pregnant Population.
MedLine Citation:
PMID:  21254924     Owner:  NLM     Status:  Publisher    
Background: Thyroid dysfunction and antibodies are increasingly recognized as risk factors during pregnancy. Thyroid function changes during pregnancy and there is a need for gestational age-specific reference intervals for thyroid hormones. The aim of this study was to calculate gestational age-specific thyrotropin (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) reference intervals in an iodine-sufficient thyroid antibody-negative population. Methods: The study population consisted of a large, prospective population-based cohort, the Northern Finland Birth Cohort 1986 (singleton births, n = 9362), with extensive data throughout gestation. The subjects underwent serum sampling in early pregnancy. Samples were assayed for TSH, fT4, fT3, thyroid-peroxidase, and thyroglobulin antibodies (n = 5805). All mothers with thyroid antibodies or previous thyroid diseases were excluded when calculating gestational age-specific percentile categories for TSH, fT4, and fT3. Also, associations between body mass index (BMI) and thyroid hormones were established. Results: The upper reference limit for TSH was 2.5 multiples of median (2.7-3.5 mU/L, depending on gestational week). The lower reference limit was as low as 0.07 mU/L. Reference intervals for fT4 rose during early pregnancy and decreased thereafter, ranging between 11-22 pmol/L. Reference intervals for fT3 were uniform throughout gestation, ranging between 3.4 and 7.0 pmol/L. BMI was associated positively with early pregnancy TSH and fT3 concentrations and negatively with fT4 concentrations. Conclusions: These gestational age-specific reference intervals for thyroid hormones provide a framework for clinical decision making. Overweight and obesity are increasing problems among fertile women and they are associated with possibility of thyroid dysfunction during pregnancy.
Tuija Männistö; Heljä-Marja Surcel; Aimo Ruokonen; Marja Vääräsmäki; Anneli Pouta; Aini Bloigu; Marjo-Riitta Järvelin; Anna-Liisa Hartikainen; Eila Suvanto
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-1-22
Journal Detail:
Title:  Thyroid : official journal of the American Thyroid Association     Volume:  -     ISSN:  1557-9077     ISO Abbreviation:  -     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2011-1-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9104317     Medline TA:  Thyroid     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1 Department of Obstetrics and Gynecology, University of Oulu , Oulu, Finland .
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