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Exploration of the optimal range of urinary iodine concentration in Chinese pregnant women in mildly iodine-deficient and -sufficient areas

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Abstract

Purpose

There is some uncertainty about the optimal ranges for urinary iodine concentration (UIC) during pregnancy. This study aimed to explore associations between maternal UIC and thyroid function in iodine sufficient and mildly iodine deficient areas.

Methods

It was a cross-sectional study in which 1461 healthy pregnant women were enrolled to collect their blood and urine samples during their routine antenatal care in Tianjin and Wuqiang, China. Wuqiang was a mildly iodine-deficient region, while Tianjin was iodine sufficient. UIC, free triiodothyronine (FT3), free thyroid hormone (FT4), thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), serum iodine concentration (SIC) including total serum iodine concentration (tSIC) and non-protein bound serum iodine concentration (nbSIC) were assessed during the routine antenatal care visits.

Results

The median UIC in pregnant women was 174 (113, 249) μg/L in Tianjin and 111 (63, 167) μg/L in Wuqiang, respectively. Compared with Tianjin, UIC, FT3 and TSH were lower, and FT4, tSIC, nbSIC, rates of TPOAb and TgAb positivity and the thyroid dysfunction rate (TDR) were higher in Wuqiang (P < 0.001). FT3, FT4, tSIC and nbSIC increased during pregnancy in Tianjin with increasing UIC, while only FT3 and nbSIC increased in Wuqiang (P < 0.05). In Tianjin, the TDR increased with UIC and peaked at UIC ≥ 500 μg/L (P = 0.002), while in Wuqiang, the TDR showed a weak “U-shaped” relationship with UIC and the rate was lowest with UIC 100–149 μg/L.

Conclusions

In iodine-deficient areas, there was a lower TDR in pregnant women with UIC 100–149 μg/L. We suspected that the optimal UIC criteria recommended by WHO may be a little high for pregnant women in mild-to-moderate iodine-deficient countries.

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Availability of data and materials

All data are available by reasonable request from the corresponding author.

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Acknowledgements

We sincerely thank all participants and clinical staff.

Funding

This work was supported by the National Natural Science Foundation of China (NSFC Grant nos. 81920108031, 71774115 and 81330064) and Program for Healthcare Reform from the Chinese National Health and Family Planning Commission (A prospective maternal and child nutrition and health cohort in China).

Author information

Author notes

  1. Yanting Chen, Wenxing Guo and Ziyun Pan contributed equally to this work.

Authors and Affiliations

  1. Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, #22 Qixiangtai Street, Heping District, Tianjin, 300070, China

    Yanting Chen, Wenxing Guo, Ziyun Pan, Dingyan Zhang, Min Gao, Wen Wu & Wanqi Zhang

  2. Department of Epidemiology and Biostatistics, School of Public Health, Guangdong Medical University, Guangdong, China

    Yanting Chen

  3. Department of Obstetrics, Tanggu Maternity Hospital, Tianjin, China

    Chongdan Wang

  4. National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, #29 Nanwei Road, Xicheng District, Beijing, 100050, China

    Yifan Duan & Jianqiang Lai

  5. Wuqiang Center for Disease Control and Prevention, Hebei, China

    Xuyang Gu

  6. Section of Endocrinology, Diabetes and Nutrition, Boston University School of Medicine, Boston, USA

    Elizabeth N. Pearce

  7. Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China

    Wanqi Zhang

  8. The Key Laboratory of Hormone and Development (Ministry of Health), Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China

    Wanqi Zhang

Authors
  1. Yanting Chen
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  2. Wenxing Guo
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  10. Elizabeth N. Pearce
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  11. Jianqiang Lai
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  12. Wanqi Zhang
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Contributions

WZ and JL conceived the study. YC, DZ, MG, WW, WG, YD, XG and CW participated in this study and collected data. ZP was responsible for the analysis of urinary and blood samples and quality control. YC and DZ analyzed the data, wrote and reviewed the paper. ENP, JL and WZ drafted the paper, all authors contributed to and approved the final draft of the manuscript.

Corresponding authors

Correspondence to Jianqiang Lai or Wanqi Zhang.

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Conflict of interest

The authors declare that they have no potential conflicts of interest.

Ethical approval

This study was approved by the Ethics Committee of Tianjin Medical University. All procedures performed in the studies were in accordance with the 1964 Helsinki declaration and its later amendments. All participants provided written informed consent prior to inclusion in the study.

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Chen, Y., Guo, W., Pan, Z. et al. Exploration of the optimal range of urinary iodine concentration in Chinese pregnant women in mildly iodine-deficient and -sufficient areas. Eur J Nutr 61, 1221–1230 (2022). https://doi.org/10.1007/s00394-021-02693-y

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  • DOI: https://doi.org/10.1007/s00394-021-02693-y

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