Changes of Thyroid Function Tests in Pregnancy and Contribution of Trimester Specific Reference Ranges to Diagnosis

Background. Due to many physiological changes during pregnancy, interpretation of thyroid function tests needs trimester-specific reference intervals for a specific population. There is no normative data documented for thyroid hormones on healthy pregnant women in Iran. The present survey was conducted to determine trimester-specific reference ranges for serum TSH, thyroxine (TT4), and triiodothyronine (TT3).Methods. The serum of 215 cases was analyzed for measurement of thyroid function tests by immunoassay method of which 152 iodine-sufficient pregnant women without thyroid autoantibodies and history of thyroid disorder or goiter were selected for final analysis. Reference intervals were defined as 5th and 95th percentiles.Results. 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), and TT3 (137.8–278.3, 154.8–327.6, and 137–323.6 ng/dl), respectively. No correlation was found between TSH and TT4 or TT3. Significant correlation was found between TT4 and TT3 in all trimesters (r=0.35,P<0.001).Conclusion. The reference intervals of thyroid function tests in pregnant women differ among trimesters. Applying trimester-specific reference ranges of thyroid hormones is warranted in order to avoid misclassification of thyroid dysfunction during pregnancy.

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Challenges in Interpretation of Thyroid Function Tests in Pregnant Women with Autoimmune Thyroid Disease

Journal of Thyroid Research ◽

10.4061/2011/598712 ◽

2011 ◽

Vol 2011 ◽

pp. 1-7 ◽

Cited By ~ 20

Author(s):

Ulla Feldt-Rasmussen ◽

Anne-Sofie Bliddal Mortensen ◽

Åse Krogh Rasmussen ◽

Malene Boas ◽

Linda Hilsted ◽

...

Keyword(s):

Thyroid Hormone ◽

Thyroid Function ◽

Thyroid Diseases ◽

Interindividual Variation ◽

Reference Ranges ◽

Thyroid Function Tests ◽

Autoimmune Thyroid ◽

Function Tests ◽

Serum Tsh ◽

In Pregnancy

Physiological changes during gestation are important to be aware of in measurement and interpretation of thyroid function tests in women with autoimmune thyroid diseases. Thyroid autoimmune activity is decreasing in pregnancy. Measurement of serum TSH is the first-line screening variable for thyroid dysfunction also in pregnancy. However, using serum TSH for control of treatment of maternal thyroid autoimmunity infers a risk for compromised foetal development. Peripheral thyroid hormone values are highly different among laboratories, and there is a need for laboratory-specific gestational age-related reference ranges. Equally important, the intraindividual variability of the thyroid hormone measurements is much narrower than the interindividual variation (reflecting the reference interval). The best laboratory assessment of thyroid function is a free thyroid hormone estimate combined with TSH. Measurement of antithyroperoxidase and/or TSH receptor antibodies adds to the differential diagnosis of autoimmune and nonautoimmune thyroid diseases.

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Young adult reference ranges for thyroid function tests on the Centaur immunoassay analyser

British Journal of Biomedical Science ◽

10.1080/09674845.2006.11732744 ◽

2006 ◽

Vol 63 (4) ◽

pp. 163-165 ◽

Cited By ~ 1

Author(s):

M. Alqahatani ◽

W. Tamimi ◽

M Aldaker ◽

F. Alenzi ◽

H. Tamim ◽

...

Keyword(s):

Young Adult ◽

Thyroid Function ◽

Reference Ranges ◽

Thyroid Function Tests ◽

Function Tests

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Gestation specific reference intervals for thyroid function tests in pregnancy

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2015-0569 ◽

2016 ◽

Vol 54 (8) ◽

Cited By ~ 6

Author(s):

Süleyman Akarsu ◽

Filiz Akbiyik ◽

Eda Karaismailoglu ◽

Zeliha Gunnur Dikmen

Keyword(s):

Pregnant Women ◽

Thyroid Function ◽

First Trimester ◽

Reference Intervals ◽

Specific Reference ◽

Thyroid Function Tests ◽

Second Trimester ◽

Third Trimester ◽

The Third ◽

Function Tests

AbstractThyroid function tests are frequently assessed during pregnancy to evaluate thyroid dysfunction or to monitor pre-existing thyroid disease. However, using non-pregnant reference intervals can lead to misclassification. International guidelines recommended that institutions should calculate their own pregnancy-specific reference intervals for free thyroxine (FT4), free triiodothyronine (FT3) and thyroid-stimulating hormone (TSH). The objective of this study is to establish gestation-specific reference intervals (GRIs) for thyroid function tests in pregnant Turkish women and to compare these with the age-matched non-pregnant women.Serum samples were collected from 220 non-pregnant women (age: 18–48), and 2460 pregnant women (age: 18–45) with 945 (39%) in the first trimester, 1120 (45%) in the second trimester, and 395 (16%) in the third trimester. TSH, FT4 and FT3 were measured using the Abbott Architect i2000SR analyzer.GRIs of TSH, FT4 and FT3 for first trimester pregnancies were 0.49–2.33 mIU/L, 10.30–18.11 pmol/L and 3.80–5.81 pmol/L, respectively. GRIs for second trimester pregnancies were 0.51–3.44 mIU/L, 10.30–18.15 pmol/L and 3.69–5.90 pmol/L. GRIs for third trimester pregnancies were 0.58–4.31 mIU/L, 10.30–17.89 pmol/L and 3.67–5.81 pmol/L. GRIs for TSH, FT4 and FT3 were different from non-pregnant normal reference intervals.TSH levels showed an increasing trend from the first trimester to the third trimester, whereas both FT4 and FT3 levels were uniform throughout gestation. GRIs may help in the diagnosis and appropriate management of thyroid dysfunction during pregnancy which will prevent both maternal and fetal complications.

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A study to establish gestation-specific reference intervals for thyroid function tests in normal singleton pregnancy

Yearbook of Pathology and Laboratory Medicine ◽

10.1016/s1077-9108(08)79068-6 ◽

2009 ◽

Vol 2009 ◽

pp. 245

Author(s):

M.G. Bissell

Keyword(s):

Thyroid Function ◽

Reference Intervals ◽

Specific Reference ◽

Thyroid Function Tests ◽

Singleton Pregnancy ◽

Function Tests

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Changes in Thyroid Function Across Adolescence: A Longitudinal Study

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/clinem/dgz331 ◽

2020 ◽

Vol 105 (4) ◽

pp. e1162-e1170 ◽

Cited By ~ 1

Author(s):

Purdey J Campbell ◽

Suzanne J Brown ◽

Phillip Kendrew ◽

Michelle Lewer ◽

Ee Mun Lim ◽

...

Keyword(s):

Thyroid Function ◽

Twin Study ◽

Specific Reference ◽

Sexually Dimorphic ◽

Reference Ranges ◽

Thyroid Function Tests ◽

Longitudinal Analyses ◽

Free Triiodothyronine ◽

Longitudinal Twin Study ◽

Abbott Architect

Abstract Objective There are no large, longitudinal studies of thyroid function across adolescence. The aims of this study were to examine longitudinal trends in thyrotropin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) and determine age-specific reference ranges. Methods Thyroid function was assessed in 3415 participants in the Brisbane Longitudinal Twin Study at ages 12, 14, and 16, using the Abbott ARCHITECT immunoassay. Longitudinal analyses were adjusted for body mass index and puberty. Results In girls, mean fT4 (± SE) increased between age 12 and 14 (by 0.30 ± 0.08 pmol/L; P < 0.001), while remaining unchanged in boys; from age 14 to 16, fT4 increased in both girls (by 0.42 ± 0.07 pmol/L; P < 0.001) and boys (0.64 ± 0.07 pmol/L, P < 0.001). There was a slight increase in fT3 from age 12 to 14 years in girls (by 0.07 ± 0.03 pmol/L; P = 0.042), with a more marked increase in boys (0.29 ± 0.03 pmol/L; P < 0.001), followed by a decrease from age 14 to 16 in both sexes (girls, by 0.53 ± 0.02 pmol/L; P < 0.001; boys, by 0.62 ± 0.03 pmol/L; P < 0.001). From age 12 to 14, TSH showed no significant change in girls or boys, then levels increased from age 14 to 16 in both sexes (in girls, by 4.9%, 95% CI: 2.4%-10.3%, P = 0.020; in boys, by 7.2%, 95% CI: 3.0%-11.6%, P = 0.001). Reference ranges differed substantially from adults, particularly for fT4 and fT3. Conclusions Thyroid function tests in adolescents display complex, sexually dimorphic patterns. Implementation of adolescence-specific reference ranges may be appropriate.

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THYROID FUNCTION IN PREGNANCY: MATERNAL AND FETAL OUTCOMES WITH HYPOTHYROIDISM AND SUBCLINICAL THYROID DYSFUNCTION

Fetal and Maternal Medicine Review ◽

10.1017/s096553951100009x ◽

2011 ◽

Vol 22 (3) ◽

pp. 169-187

Author(s):

NEIL K VANES ◽

JOHN H LAZARUS ◽

SHIAO-Y CHAN

Keyword(s):

Thyroid Hormones ◽

Pregnant Women ◽

Thyroid Function ◽

Thyroid Dysfunction ◽

Thyroid Disorders ◽

Thyroid Function Tests ◽

Fetal Outcomes ◽

Function Tests ◽

Maternal Wellbeing ◽

In Pregnancy

Thyroid hormones are important in the development of the fetus and the placenta as well as in maintaining maternal wellbeing. Thyroid disorders are common in the population as a whole, particularly in women, and therefore are common during pregnancy and the puerperium. Biochemical derangement of thyroid function tests are present in approximately 2.5–5% of pregnant women.

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