Authors
Affiliations
Department of Midwifery, Varamin-Pishva Branch, Islamic Azad University, Tehran, Iran; Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- 1Prevention of Metabolic Disorders Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- 2Tehran University of Medical Sciences, Tehran, Iran.
- 3Department of Biostatistics and Epidemiology, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- 4Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- 5Prevention of Metabolic Disorders Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. fzhadaegh@endocrine.ac.ir.
Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Midwifery and Reproductive Health Research Center, Department of Midwifery and Reproductive Health, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran; Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
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Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Abstract
Objective: Physiological gestational changes are associated with alterations in thyroid function which require different biochemical interpretation from that of non-pregnant women and necessitate established pregnancy-specific reference ranges. We aimed to identify the trimester-specific ranges of thyroid markers in a healthy population of pregnant Iranian women.
Methods: In this self-sequential study, data were extracted from The Tehran Thyroid and Pregnancy Study; a total of 314 women were tested during the 1st, 2nd and 3rd trimesters for serum levels of thyrotropin (TSH), thyroxine (T4), free thyroxine index (FT4I) and thyroid peroxidase antibody (TPOAb). Trimester-specific reference intervals for TSH, T4 and FT4I and first trimester reference range for TPOAb were estimated. The normal and modulus exponential-normal models were fitted by maximum likelihood using STATA software. The 2.5th and 97.5th percentiles of thyroid parameters were determined and used as reference intervals.
Results: Mean±SD age of participants was 26.8±5.2years. Estimated reference intervals for TSH, T4 and FT4I in the 1st, 2nd and 3rd trimesters corresponding to the 2.5th and 97.5th percentiles were 0.14-6.14, 0.43-4.64, 0.63-3.9μIU/ml; 78.01-215.19, 93.23-243.87, 89.61-211.37nmol/L; and 1.73-4.53, 1.96-5.64, 1.72-4.30, respectively. Reference interval for TPOAb in the 1st trimester was 1.40-38.02IU/mL. Median of TSH was low in the 1st trimester, and gradually increased until 2nd trimester, followed by a slight decrease onward. A decreasing trend in TSH levels was observed in higher centiles with advancing gestational age.
Conclusion: This study provides trimester-specific reference ranges for some common thyroid markers among healthy Iranian women in an iodine sufficient area, to prevent biochemical misinterpretations during pregnancy.