Serum thyroid hormone levels among Chinese pregnant women

Abstract

Aim: The aim of this study is to examine gestational serum thyroid hormone levels and influencing factors among Chinese pregnant women with high dietary iodine intake.

Methods: The study was conducted from 2011 and 2013 in Zhoushan Women & Children’s Hospital, Zhejiang, China. A total of 1991 pregnant women were enrolled and their serum levels of free thyroid hormones (FT₄, FT₃, and TSH) were detected by chemiluminescence method.

Results: Gestational serum FT₄ and FT₃ decreased with gestational week while TSH increased. Furthermore, the prevalence rate of subclinical hypothyroid increased with gestational stages, especially in the third trimester. Women aged more than 30 years had lower FT₄ and FT₃ in the first trimester and lower FT₄ in the second trimester. No significant difference was found in the association of gestational serum thyroid hormones with maternal height and the gender of fetuses.

Conclusion: Gestational serum thyroid hormones significantly changed with gestational week and were associated with the age of women. Specific normal range of thyroid hormones might be modified so as to better evaluate the thyroid hormone levels of pregnant women during pregnancy.

Chinese abstract

目的：本研究的目的是检测中国高饮食碘摄入的妊娠期女性血清甲状腺激素水平及其影响因素。

方法：该项研究于2011年至2013年在中国浙江舟山妇女儿童医院开展, 共检测了1991名孕妇的血清游离甲状腺激素水平（FT4, FT3, TSH）。

结果：妊娠期女性血清FT4和FT3水平降低, TSH水平升高。另外, 亚临床甲状腺功能亢进的发病率随孕周增加而增加, 特别是在妊娠晚期。30岁以上的妊娠期女性, 在孕早期FT4和FT3水平较低, 孕中期FT4水平较低。妊娠期血清甲状腺激素水平与孕妇身高和胎儿性别无明显关系。

结论：妊娠期女性血清甲状腺激素变化与孕周以及孕妇的年龄有关。甲状腺激素的正常范围应进行相应调整, 以更好地评估妊娠期女性的甲状腺激素水平。

Keywords:

• FT₄
• FT₃
• pregnant women
• thyroid hormones
• TSH

Acknowledgements

The authors thank the support from participants and their families.

Declaration of interest

The authors report no conflicts of interest. This study was funded by grants from Natural Science Foundation of Zhejiang Province in China (Grant nos. LY14H260003 and Y20100505).