| Establishment of the trimester-specific reference range for free thyroxine index. | |
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MedLine Citation:
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PMID: 23167270 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Abstract Background: Accurate assessment of thyroid status during pregnancy is vital for maternal and fetal health. Because free T4 (FT4) values in pregnancy vary widely between methods, assessment of total thyroxine (TT4) and free T4 index (FT4I) may be superior to FT4 in pregnant women. However, trimester-specific reference intervals for FT4I have not yet been established. In this longitudinal self-sequential survey, we aimed at determining the trimester-specific reference range for FT4I in healthy Iranian women with singleton pregnancies. Methods: A total of 466 healthy pregnant women were evaluated. After exclusion of women with history, ultrasonographic or laboratory evidence of any thyroid disorder or iodine deficiency and those who were positive for TPO Ab or Tgb Ab, 152 women entered the study. Serum TSH, TT4, triiodthyronin (TT3) and T3-resine uptake (T3RU) were measured by the immunoassay method. Reference intervals were defined as 5th and 95th percentiles, using the bootstrap based procedure. Results: Mean values in the first, second and third trimesters were: 1.7±1.5, 1.9±1.8 and 1.9±1.8 mIU/l for TSH; 12.9±3, 14.4±3.1and 13.6±3.3 µg/dl for TT4; 198±43, 229±53 and 230±53ng/dl for TT3; 25.2±3.8, 22.4±3.1 and 22.4±3.2% for T3RU and 12.8±3.5, 14.2±3.3 and 13.5±3.8 for FT4I, respectively. Reference intervals in the first, second and third trimesters were as follows: TSH (0.2-3.9 , 0.5-4.1 and 0.6-4.1 mIU/l); TT4(8.2-18.5,10.1- 20.6 and 9-19.4 µg/dl); TT3(137-278,154-327and 137-323 ng/dl); T3RU( 19.3-31.2, 18.2-28.2,17.6-28.9%) and FT4I(8.5-19 , 9.7-21, 8.7-20.4), respectively. Serum TSH had no significant correlation with TT4 or TT3. Serum TSH had a significant but weak correlation with FT4I only in the first trimester (r=-0.24, p=0.006). Conclusion: This study, for the first time, establishes the trimester-specific reference intervals for FT4I in a reference population of normal pregnant Iranian women. |
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Authors:
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Fereidoun Azizi; Ladan Mehran; Atieh Amouzegar; Hossein Delshad; Maryam Tohidi; Sahar Askari; Mehdi Hedayati |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-11-20 |
Journal Detail:
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Title: Thyroid : official journal of the American Thyroid Association Volume: - ISSN: 1557-9077 ISO Abbreviation: Thyroid Publication Date: 2012 Nov |
Date Detail:
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Created Date: 2012-11-21 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9104317 Medline TA: Thyroid Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences,, Tehran, Iran, Islamic Republic of; azizi@endocrine.ac.ir. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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