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Salivary iodine concentration in pregnant women and its association with iodine status and thyroid function

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Abstract

Purpose

There have been no reports on the application of salivary iodine concentration (SIC) in evaluating iodine nutrition in pregnant women. This study aimed to clarify the relationship between SIC and indicators of iodine nutritional status and thyroid function during pregnancy, to investigate whether salivary iodine can be applied to the evaluation of iodine nutritional status in pregnant women, and to provide a reference basis for establishing a normal range of salivary iodine values during pregnancy.

Methods

Pregnant women were enrolled in the Department of Obstetrics, the people’s hospital of Yuncheng Country, Shandong Province, from July 2021 to December 2022, using random cluster sampling. Saliva, urine, and blood samples were collected from pregnant women to assess iodine nutritional status, and venous blood was collected to determine thyroid function.

Results

A total of 609 pregnant women were included in this study. The median spot urinary iodine concentration (SUIC) was 261 μg/L. The median SIC was 297 μg/L. SIC was positively correlated with SUIC (r = 0.46, P < 0.0001), 24-h UIC (r = 0.30, P < 0.0001), 24-h urinary iodine excretion (24-h UIE) (r = 0.41, P < 0.0001), and estimated iodine intake (EII) (r = 0.52, P < 0.0001). After adjusting for confounders, there was a weak correlation between SIC and serum total iodine and serum non-protein-bound iodine (P = 0.02, P = 0.04, respectively). Pregnant women with a SIC < 176 μg/L had a higher risk of insufficient iodine status (OR = 2.07, 95% CI 1.35–3.19) and thyroid dysfunction (OR = 2.71, 95% CI 1.18–6.21) compared to those with higher SIC. Those having SIC > 529 μg/L were more likely to have excessive iodine status (OR = 2.82, 95% CI 1.81–4.38) and thyroid dysfunction (OR = 3.04, 95% CI 1.36–6.78) than those with lower SIC values.

Conclusion

SIC is associated with urinary iodine concentration and thyroid function in pregnant women. SIC < 176 μg/L was associated with an increased risk for iodine deficiency and hypothyroxinemia, while SIC > 529 μg/L was related to excess and thyrotoxicosis. SIC can be used as a reference indicator for evaluating the iodine nutrition status of pregnant women, but it needs further investigation and verification.

Trial registration

NCT04492657(Aug 9, 2022).

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Data availability

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

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Acknowledgements

The authors thank the Yuncheng County People’s Hospital for their support and help in field investigations. They appreciate the co-cooperation and participations of teachers, nurses, and pregnant women.

Funding

This work was supported by the National Natural Science Foundation of China (NSFC Grant no. 81920108031 and 82230113).

Author information

Author notes

  1. Shaohan Li and Wenxing Guo should be considered joint first author.

Authors and Affiliations

  1. Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, 300070, China

    Shaohan Li, Wenxing Guo, Qi Jin, Qi Meng, Rui Yang, Hexi Zhang, Min Fu & Wanqi Zhang

  2. Department of Obstetrics, Yuncheng County People’s Hospital, Yuncheng, 274700, China

    Ting Wang

  3. Department of Clinical Laboratory, Yuncheng County People’s Hospital, Yuncheng, 274700, China

    Denghai Liu & Xianglu Meng

  4. Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China

    Wanqi Zhang

  5. Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, 300070, China

    Wanqi Zhang

  6. Tianjin Key Laboratory of Hormones and Development (Ministry of Health), Tianjin, 300384, China

    Wanqi Zhang

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Contributions

ZW designed the research. LS performed the field investigation, the data analysis, and wrote the paper. GW took part in the data analysis and paper writing. JQ, MQ, YR, FM, and WT performed the field investigation and collected the data. ZH, LD, and MX performed the laboratory analysis. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Wanqi Zhang.

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Conflict of interest

The authors declare that they have no conflict of interest.

Ethical standards

This study was approved by the Ethics Committee of Tianjin Medical University (serial number: TMUhMEC2020033). All procedures performed in the studies were in accordance with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All participants provided an informed consent after receiving a full explanation of the purpose and procedure of the study.

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Li, S., Guo, W., Jin, Q. et al. Salivary iodine concentration in pregnant women and its association with iodine status and thyroid function. Eur J Nutr (2024). https://doi.org/10.1007/s00394-024-03332-y

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