Longitudinal assessment of thyroid function in pregnancy

Elif I. Ekinci, Zhong X. Lu, Ken Sikaris, Intissar Bittar, Karey Y. Cheong, Que Lam, Nick Crinis, Christine A. Houlihan

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Background: Trimester-specific reference intervals (RIs) for thyroid function tests are lacking for Beckman Dxl 800 analysers. We aimed to establish RIs for thyroid stimulating hormone (TSH), free thyroxine (fT4) and to track intraindividual changes in thyroid function throughout pregnancy. Methods: One hundred and thirty healthy women without antithyroid peroxidase antibodies were followed longitudinally. Thyroid function was determined at trimester-1 (T1): 9-13 weeks; trimester-2 (T2): 22-26 weeks; trimester-3 (T3): 35-39 weeks and postpartum (PP): 8-12 weeks. A subgroup (n 1/4 47) was used to track intraindividual changes using PP as non-pregnant state (baseline). Results: For trimesters 1-3, TSH (median (2.5th, 5th, 95th and 97.5th percentile)) was 0.77 (0.03, 0.05, 2.33, 3.05), 1.17 (0.42, 0.47, 2.71, 3.36) and 1.35 (0.34, 0.42, 2.65, 2.83) mIU/L, respectively. Free T4 (mean (95%CI)) was 10.7 (5.9-15.5), 8.1 (4.9-11.3), 7.8 (4.5-11.0) pmol/L, respectively. In T2 and T3, 36% and 41% of the fT4 values, respectively, fell below the non-pregnancy lower normal limit. In the subgroup assessed for longitudinal changes, of the women with baseline TSH 4 median, 71-75% remained at or below the corresponding median for trimesters 1-3. Of the women with baseline fT4 4 median, 69-81% also remained at or below the corresponding median for trimesters 1-3. High correlation was observed at different trimesters and baseline for TSH (Spearman's r: 0.593-0.846, P < 0.001) and for fT4 (r: 0.480-0.739, P< 0.001). Conclusions: Use of trimester-specific RIs would prevent misclassification of thyroid function during pregnancy. In the majority of women, TSH and fT4 tracked on the same side of the median distribution, from a non-pregnant baseline, throughout pregnancy.

Original languageEnglish
Pages (from-to)595-602
Number of pages8
JournalAnnals of Clinical Biochemistry
Volume50
Issue number6
DOIs
Publication statusPublished - 2013

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Thyrotropin
Thyroid Gland
Pregnancy
Postpartum Period
Thyroid Function Tests
Thyroxine
Peroxidase
Antibodies

Cite this

Ekinci, E. I., Lu, Z. X., Sikaris, K., Bittar, I., Cheong, K. Y., Lam, Q., ... Houlihan, C. A. (2013). Longitudinal assessment of thyroid function in pregnancy. Annals of Clinical Biochemistry, 50(6), 595-602. https://doi.org/10.1177/0004563213486450
Ekinci, Elif I. ; Lu, Zhong X. ; Sikaris, Ken ; Bittar, Intissar ; Cheong, Karey Y. ; Lam, Que ; Crinis, Nick ; Houlihan, Christine A. / Longitudinal assessment of thyroid function in pregnancy. In: Annals of Clinical Biochemistry. 2013 ; Vol. 50, No. 6. pp. 595-602.
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title = "Longitudinal assessment of thyroid function in pregnancy",
abstract = "Background: Trimester-specific reference intervals (RIs) for thyroid function tests are lacking for Beckman Dxl 800 analysers. We aimed to establish RIs for thyroid stimulating hormone (TSH), free thyroxine (fT4) and to track intraindividual changes in thyroid function throughout pregnancy. Methods: One hundred and thirty healthy women without antithyroid peroxidase antibodies were followed longitudinally. Thyroid function was determined at trimester-1 (T1): 9-13 weeks; trimester-2 (T2): 22-26 weeks; trimester-3 (T3): 35-39 weeks and postpartum (PP): 8-12 weeks. A subgroup (n 1/4 47) was used to track intraindividual changes using PP as non-pregnant state (baseline). Results: For trimesters 1-3, TSH (median (2.5th, 5th, 95th and 97.5th percentile)) was 0.77 (0.03, 0.05, 2.33, 3.05), 1.17 (0.42, 0.47, 2.71, 3.36) and 1.35 (0.34, 0.42, 2.65, 2.83) mIU/L, respectively. Free T4 (mean (95{\%}CI)) was 10.7 (5.9-15.5), 8.1 (4.9-11.3), 7.8 (4.5-11.0) pmol/L, respectively. In T2 and T3, 36{\%} and 41{\%} of the fT4 values, respectively, fell below the non-pregnancy lower normal limit. In the subgroup assessed for longitudinal changes, of the women with baseline TSH 4 median, 71-75{\%} remained at or below the corresponding median for trimesters 1-3. Of the women with baseline fT4 4 median, 69-81{\%} also remained at or below the corresponding median for trimesters 1-3. High correlation was observed at different trimesters and baseline for TSH (Spearman's r: 0.593-0.846, P < 0.001) and for fT4 (r: 0.480-0.739, P< 0.001). Conclusions: Use of trimester-specific RIs would prevent misclassification of thyroid function during pregnancy. In the majority of women, TSH and fT4 tracked on the same side of the median distribution, from a non-pregnant baseline, throughout pregnancy.",
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Ekinci, EI, Lu, ZX, Sikaris, K, Bittar, I, Cheong, KY, Lam, Q, Crinis, N & Houlihan, CA 2013, 'Longitudinal assessment of thyroid function in pregnancy', Annals of Clinical Biochemistry, vol. 50, no. 6, pp. 595-602. https://doi.org/10.1177/0004563213486450

Longitudinal assessment of thyroid function in pregnancy. / Ekinci, Elif I.; Lu, Zhong X.; Sikaris, Ken; Bittar, Intissar; Cheong, Karey Y.; Lam, Que; Crinis, Nick; Houlihan, Christine A.

In: Annals of Clinical Biochemistry, Vol. 50, No. 6, 2013, p. 595-602.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Longitudinal assessment of thyroid function in pregnancy

AU - Ekinci, Elif I.

AU - Lu, Zhong X.

AU - Sikaris, Ken

AU - Bittar, Intissar

AU - Cheong, Karey Y.

AU - Lam, Que

AU - Crinis, Nick

AU - Houlihan, Christine A.

PY - 2013

Y1 - 2013

N2 - Background: Trimester-specific reference intervals (RIs) for thyroid function tests are lacking for Beckman Dxl 800 analysers. We aimed to establish RIs for thyroid stimulating hormone (TSH), free thyroxine (fT4) and to track intraindividual changes in thyroid function throughout pregnancy. Methods: One hundred and thirty healthy women without antithyroid peroxidase antibodies were followed longitudinally. Thyroid function was determined at trimester-1 (T1): 9-13 weeks; trimester-2 (T2): 22-26 weeks; trimester-3 (T3): 35-39 weeks and postpartum (PP): 8-12 weeks. A subgroup (n 1/4 47) was used to track intraindividual changes using PP as non-pregnant state (baseline). Results: For trimesters 1-3, TSH (median (2.5th, 5th, 95th and 97.5th percentile)) was 0.77 (0.03, 0.05, 2.33, 3.05), 1.17 (0.42, 0.47, 2.71, 3.36) and 1.35 (0.34, 0.42, 2.65, 2.83) mIU/L, respectively. Free T4 (mean (95%CI)) was 10.7 (5.9-15.5), 8.1 (4.9-11.3), 7.8 (4.5-11.0) pmol/L, respectively. In T2 and T3, 36% and 41% of the fT4 values, respectively, fell below the non-pregnancy lower normal limit. In the subgroup assessed for longitudinal changes, of the women with baseline TSH 4 median, 71-75% remained at or below the corresponding median for trimesters 1-3. Of the women with baseline fT4 4 median, 69-81% also remained at or below the corresponding median for trimesters 1-3. High correlation was observed at different trimesters and baseline for TSH (Spearman's r: 0.593-0.846, P < 0.001) and for fT4 (r: 0.480-0.739, P< 0.001). Conclusions: Use of trimester-specific RIs would prevent misclassification of thyroid function during pregnancy. In the majority of women, TSH and fT4 tracked on the same side of the median distribution, from a non-pregnant baseline, throughout pregnancy.

AB - Background: Trimester-specific reference intervals (RIs) for thyroid function tests are lacking for Beckman Dxl 800 analysers. We aimed to establish RIs for thyroid stimulating hormone (TSH), free thyroxine (fT4) and to track intraindividual changes in thyroid function throughout pregnancy. Methods: One hundred and thirty healthy women without antithyroid peroxidase antibodies were followed longitudinally. Thyroid function was determined at trimester-1 (T1): 9-13 weeks; trimester-2 (T2): 22-26 weeks; trimester-3 (T3): 35-39 weeks and postpartum (PP): 8-12 weeks. A subgroup (n 1/4 47) was used to track intraindividual changes using PP as non-pregnant state (baseline). Results: For trimesters 1-3, TSH (median (2.5th, 5th, 95th and 97.5th percentile)) was 0.77 (0.03, 0.05, 2.33, 3.05), 1.17 (0.42, 0.47, 2.71, 3.36) and 1.35 (0.34, 0.42, 2.65, 2.83) mIU/L, respectively. Free T4 (mean (95%CI)) was 10.7 (5.9-15.5), 8.1 (4.9-11.3), 7.8 (4.5-11.0) pmol/L, respectively. In T2 and T3, 36% and 41% of the fT4 values, respectively, fell below the non-pregnancy lower normal limit. In the subgroup assessed for longitudinal changes, of the women with baseline TSH 4 median, 71-75% remained at or below the corresponding median for trimesters 1-3. Of the women with baseline fT4 4 median, 69-81% also remained at or below the corresponding median for trimesters 1-3. High correlation was observed at different trimesters and baseline for TSH (Spearman's r: 0.593-0.846, P < 0.001) and for fT4 (r: 0.480-0.739, P< 0.001). Conclusions: Use of trimester-specific RIs would prevent misclassification of thyroid function during pregnancy. In the majority of women, TSH and fT4 tracked on the same side of the median distribution, from a non-pregnant baseline, throughout pregnancy.

KW - Beckman Dxl 800 analyser

KW - Free T3

KW - Free T4

KW - Pregnancy

KW - Thyroid function

KW - Thyroid stimulating hormone

KW - Trimester-specific reference intervals

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DO - 10.1177/0004563213486450

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Ekinci EI, Lu ZX, Sikaris K, Bittar I, Cheong KY, Lam Q et al. Longitudinal assessment of thyroid function in pregnancy. Annals of Clinical Biochemistry. 2013;50(6):595-602. https://doi.org/10.1177/0004563213486450