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The correlation between the thyroid function and urinary iodine/creatinine ratio of pregnant women attending a tertiary hospital in Beijing, China, during different trimesters

BMC Endocrine Disorders volume 24, Article number: 171 (2024) Cite this article

Abstract

Objective

This study investigated the correlation between thyroid function and urinary iodine/creatinine ratio (UI/Cr) in pregnant women during different trimesters and explored potential influencing factors.

Methods

In this cross-sectional study, serum levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), and UI/Cr were measured in 450 pregnant women. Correlations were analyzed using Pearson’s correlation coefficient and multiple linear regression. Subgroup analyses were performed based on age, body mass index (BMI), parity, gestational age, education, occupation, and family history of thyroid disorders.

Results

UI/Cr was positively correlated with FT4 levels in the first and second trimesters, particularly in women with older age, higher BMI, multiparity, higher education, and employment. No significant correlations were found between UI/Cr and TSH or FT3 levels.

Conclusion

UI/Cr is positively correlated with FT4 levels in early pregnancy, especially in women with certain risk factors. Regular monitoring of iodine status and thyroid function is recommended for pregnant women to ensure optimal maternal and fetal health.

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Introduction

Thyroid disorders are among the most common endocrine disorders during pregnancy, with an estimated prevalence of 2–3% [1,2,3,4]. Thyroid hormones play a crucial role in fetal growth and neurodevelopment, and maternal thyroid dysfunction has been associated with various adverse pregnancy outcomes, such as miscarriage, preterm delivery, gestational hypertension, and impaired fetal neurodevelopment [5, 6]. Iodine is an essential micronutrient for thyroid hormone synthesis, and iodine deficiency during pregnancy can lead to hypothyroidism and its associated complications [7]. On the other hand, excessive iodine intake can also disrupt thyroid function and lead to hypothyroidism or hyperthyroidism [8]. Therefore, maintaining optimal iodine status during pregnancy is of utmost importance for ensuring healthy thyroid function and fetal development.

Urinary iodine concentration (UIC) is the most widely used biomarker for assessing iodine status in populations [9]. However, UIC can be influenced by various factors, such as hydration status, renal function, and the timing of urine collection, which can lead to inaccurate estimates of iodine status [10]. To overcome these limitations, the urinary iodine/creatinine ratio (UI/Cr) has been proposed as a more reliable marker of iodine status, as it takes into account the variation in urine volume and creatinine excretion [11]. UI/Cr has been shown to correlate well with 24-hour urinary iodine excretion, which is considered the gold standard for assessing iodine status [12].

Previous studies have investigated the relationship between iodine status and thyroid function during pregnancy, but the results have been inconsistent and inconclusive [13,14,15]. Some studies have reported a positive correlation between UI/Cr and free thyroxine (FT4) levels, while others have found no significant association. Moreover, the correlation between UI/Cr and thyroid function may vary depending on the stage of pregnancy, as the thyroid gland undergoes significant changes throughout gestation [16]. In early pregnancy, there is an increase in thyroid hormone production due to the stimulatory effect of human chorionic gonadotropin (hCG) on the thyroid gland [17]. In contrast, in late pregnancy, there is a physiological increase in serum thyroxine-binding globulin (TBG) levels, which can lead to a decrease in free thyroid hormone levels [18].

The potential mechanisms underlying the observed correlations between UI/Cr and FT4 levels in the first and second trimesters may involve several factors. The stimulatory effect of hCG on the thyroid gland in early pregnancy may increase thyroid hormone production and the demand for iodine [1]. The physiological changes in thyroid hormone metabolism during pregnancy, such as the increased TBG levels and the increased activity of placental deiodinases, may also influence the relationship between iodine status and thyroid function [3].

In addition to the stage of pregnancy, other factors such as age, body mass index (BMI), parity, gestational age, education level, occupation, and family history of thyroid disorders may also influence the relationship between iodine status and thyroid function [19,20,21]. For example, older women and those with higher BMI are at increased risk of thyroid disorders, and multiparity has been associated with a higher prevalence of thyroid autoimmunity [22]. Similarly, gestational age may affect thyroid function, as the fetal thyroid gland starts to produce thyroid hormones from the second trimester onwards [23]. Education level and occupation may also influence iodine status and thyroid function, as they may be associated with differences in dietary habits and access to healthcare [24, 25].

While previous studies have established a correlation between urinary iodine and thyroid function, the relationship between UI/Cr ratio and thyroid function parameters during different trimesters of pregnancy remains understudied, particularly in the context of a large urban Chinese population. This study was conducted in Beijing, China, a region of particular interest due to its large urban population and changing dietary patterns. China has implemented a universal salt iodization program since 1995, but iodine status can still vary significantly in different regions and populations. Understanding the iodine status and thyroid function of pregnant women in this urban setting can provide valuable insights for public health strategies and clinical management in similar populations.Our study aims to address this gap by investigating the trimester-specific correlations between UI/Cr ratio and thyroid function parameters, as well as exploring potential influencing factors.

The findings of this study may provide valuable insights into the relationship between iodine status and thyroid function during pregnancy and inform clinical practice guidelines for monitoring and managing thyroid disorders in pregnant women. The potential mechanisms underlying the observed correlations will also be explored based on the current understanding of thyroid physiology during pregnancy.

Methods

Study design and participants

This cross-sectional study was conducted at a tertiary hospital in Beijing, China, from January 2020 to December 2020. The study population consisted of pregnant women who attended the antenatal clinic for routine checkups during the study period. The inclusion criteria were: (1) age between 18 and 40 years; (2) singleton pregnancy; (3) no history of thyroid disorders or other chronic diseases; and (4) no use of iodine-containing supplements or medications. The exclusion criteria were: (1) multiple pregnancies; (2) gestational age less than 4 weeks or more than 42 weeks; (3) presence of other endocrine disorders or autoimmune diseases; and (4) incomplete data or lost to follow-up.

The sample size was calculated based on the expected correlation coefficient between UI/Cr and FT4 levels of 0.2, with a power of 80% and a significance level of 0.05. A minimum sample size of 193 pregnant women was required for each trimester. Considering a potential dropout rate of 20%, a total of 750 pregnant women were initially recruited for the study, with 250 women in each trimester (first trimester: 4–13 weeks; second trimester: 14–27 weeks; third trimester: 28–42 weeks). After excluding those with incomplete data or lost to follow-up, the final study sample consisted of 450 pregnant women, with 150 women in each trimester.

The study was approved by the Ethics Committee of Beijing Friendship Hospital (ethical batch number: BJFH-EC/2013-011), and all participants provided written informed consent before enrollment. The study was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines [26, 27].

Data collection

Demographic and clinical data, including age, gestational age, body mass index (BMI), parity, education level, occupation, and family history of thyroid disorders, were collected using a structured questionnaire administered by trained interviewers. Gestational age was determined based on the last menstrual period and confirmed by ultrasound examination.

Blood and urine samples were collected from each participant during their routine antenatal visits. Blood samples were collected in the morning after an overnight fast and centrifuged within 2 h of collection. Serum was separated and stored at -80 °C until analysis. Urine samples were collected in the morning, preferably from the first morning void, and stored at -20 °C until analysis.

Serum levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were measured using chemiluminescent immunoassays (Cobas e601, Roche Diagnostics, Switzerland) according to the manufacturer’s instructions. The reference ranges for TSH, FT3, and FT4 were 0.27–4.2 mIU/L, 3.1–6.8 pmol/L, and 12–22 pmol/L, respectively [28]. The intra-assay and inter-assay coefficients of variation were less than 5% for all thyroid function tests.

Urinary iodine concentration (UIC) was measured using the ammonium persulfate digestion method followed by the Sandell-Kolthoff reaction, as recommended by the World Health Organization (WHO) [29]. Urinary creatinine concentration was measured using the Jaffe reaction method [30]. The UI/Cr was calculated by dividing the UIC (µg/L) by the urinary creatinine concentration (g/L) and expressed as µg/g. The WHO recommends a median UI/Cr of 150–249 µg/g as the optimal range for pregnant women [31].

Statistical analysis

Data were analyzed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA). Continuous variables were presented as mean ± standard deviation (SD) or median (interquartile range, IQR), and categorical variables were presented as frequencies and percentages. The normality of the data was assessed using the Kolmogorov-Smirnov test.

The correlation between UI/Cr and thyroid function parameters (TSH, FT3, and FT4) was analyzed using Pearson’s correlation coefficient for normally distributed data and Spearman’s rank correlation coefficient for non-normally distributed data. Multiple linear regression analysis was performed to identify the independent factors associated with thyroid function parameters, with UI/Cr, age, BMI, parity, education level, occupation, and family history of thyroid disorders as the independent variables.

Subgroup analyses were performed based on age (< 35 years vs. ≥35 years), BMI (< 25 kg/m2 vs. ≥25 kg/m2), parity (nulliparous vs. multiparous), gestational age (first trimester vs. second trimester vs. third trimester), education level (high school or below vs. college or above), occupation (employed vs. unemployed), and family history of thyroid disorders (yes vs. no) to explore the potential factors influencing the correlation between UI/Cr and thyroid function.

A two-tailed P-value of less than 0.05 was considered statistically significant.

Results

Participant characteristics

The mean age of the participants was 29.6 ± 4.2 years, and the mean gestational age was 20.4 ± 9.1 weeks. The majority of the participants had a normal BMI (68.2%), were nulliparous (64.4%), had a college education or above (76.0%), and were employed (72.4%). A family history of thyroid disorders was reported by 8.4% of the participants.

The median UI/Cr was 146.7 µg/g (IQR: 102.4–210.5 µg/g) in the first trimester, 165.2 µg/g (IQR: 115.8–235.7 µg/g) in the second trimester, and 158.9 µg/g (IQR: 110.2–227.6 µg/g) in the third trimester. The median UI/Cr was highest in the second trimester and lowest in the first trimester, but the difference was not statistically significant (P = 0.078).

Pearson’s correlation analysis showed a significant positive correlation between UI/Cr and FT4 levels in the first (r = 0.168, P = 0.025) and second trimesters (r = 0.205, P = 0.005) (Table 1). However, no significant correlation was observed between UI/Cr and FT4 levels in the third trimester (r = 0.139, P = 0.090). Additionally, no significant correlations were found between UI/Cr and TSH or FT3 levels in any trimester (all P > 0.05).

Table 1 Correlation between UI/Cr and thyroid function parameters in different trimesters
Full size table

These findings suggest that iodine status, as indicated by UI/Cr, influence thyroid function differently across trimesters, with the strongest association observed in the second trimester.

Multiple linear regression analysis

Multiple linear regression analysis showed that UI/Cr was an independent factor positively associated with FT4 levels in the first (β = 0.168, P = 0.025) and second trimesters (β = 0.205, P = 0.005), after adjusting for age, BMI, parity, education level, occupation, and family history of thyroid disorders (Table 2). No significant association was found between UI/Cr and TSH or FT3 levels in any trimester.

Table 2 Multiple linear regression analysis of factors associated with FT4 levels in different trimesters
Full size table

These results further support the trimester-specific relationship between iodine status and thyroid function, particularly FT4 levels.

Subgroup analyses

Subgroup analyses revealed that the correlation between UI/Cr and FT4 levels was more pronounced in women with older age (≥ 35 years), higher BMI (≥ 25 kg/m2), multiparity, higher education level (college or above), and employment (Table 3). The correlation was also stronger in the second trimester compared to the first and third trimesters. No significant difference in the correlation between UI/Cr and FT4 levels was observed based on family history of thyroid disorders.

Table 3 Subgroup analyses of the correlation between UI/Cr and FT4 levels in different trimesters
Full size table

Subgroup findings suggest that demographic and clinical factors influence the relationship between iodine status and thyroid function during pregnancy, potentially identifying groups that require closer monitoring or targeted interventions.

Discussion

This study examined the correlation between thyroid function and UI/Cr in pregnant women across trimesters in Beijing, China, and explored influencing factors. UI/Cr was positively correlated with FT4 levels in the first and second trimesters, but not in the third. No significant correlation was found between UI/Cr and TSH or FT3 levels in any trimester. The correlation was more pronounced in women with older age, higher BMI, multiparity, higher education level, and employment.

The positive correlation in early pregnancy suggests iodine status may influence thyroid function, consistent with previous studies [32, 33]. Chen et al. found pregnant women with adequate iodine status had higher FT4 levels in the first and second trimesters [34]. Zimmermann et al. reported iodine supplementation during pregnancy increased FT4 levels and reduced hypothyroidism risk [35].

The lack of correlation in the third trimester may be due to physiological changes. Increased serum TBG levels can decrease free thyroid hormone levels [18], potentially masking iodine status effects. Additionally, fetal thyroid hormone production starting from the second trimester [23] may contribute to this lack of correlation.

The lack of correlation between UI/Cr and TSH or FT3 levels in any trimester aligns with previous studies [36, 37]. Glinoer et al. found no significant difference in TSH levels between pregnant women with adequate iodine status and those with deficiency [38]. Li et al. reported no significant correlation between UI/Cr and FT3 levels in pregnant women [39].

These findings have important clinical implications for managing thyroid disorders during pregnancy. Regular monitoring of iodine status and thyroid function is recommended, especially for those with risk factors. Iodine supplementation may be considered for deficient women to prevent hypothyroidism and associated adverse outcomes [40]. However, excessive iodine intake should be avoided as it can disrupt thyroid function [41].

This study has several strengths, including the large sample size, the inclusion of pregnant women from all trimesters, and the use of UI/Cr as a reliable marker of iodine status. The study also explored the potential factors influencing the correlation between UI/Cr and thyroid function, which provides valuable insights into the management of thyroid disorders during pregnancy. The potential mechanisms underlying the observed correlations were also discussed based on the current understanding of thyroid physiology during pregnancy.

However, the study also has some limitations. First, the cross-sectional design of the study does not allow for the assessment of causal relationships between iodine status and thyroid function. Second, the study was conducted in a single tertiary hospital in Beijing, China, and the findings may not be generalizable to other populations or settings. Third, while we excluded women using iodine-containing supplements, we did not assess dietary iodine intake, which may have influenced the results. Fourth, the study did not assess thyroid autoimmunity, which is a common cause of thyroid dysfunction during pregnancy [42]. Fifth, the study did not assess the long-term outcomes of the pregnant women and their offspring, which may be influenced by thyroid function during pregnancy [43].

Future studies with a prospective design, larger sample sizes, and more diverse populations are needed to confirm and extend the findings of this study. Studies that assess the dietary iodine intake and the use of iodine-containing supplements or medications are also needed to provide a more comprehensive understanding of the relationship between iodine status and thyroid function during pregnancy. Studies that assess thyroid autoimmunity and the long-term outcomes of the pregnant women and their offspring are also warranted to inform clinical practice guidelines for the management of thyroid disorders during pregnancy.

In conclusion, this study found a positive correlation between UI/Cr and FT4 levels in the first and second trimesters of pregnancy, particularly in women with older age, higher BMI, multiparity, higher education level, and employment. Regular monitoring of iodine status and thyroid function is recommended for pregnant women to ensure optimal maternal and fetal health, especially for those with risk factors for thyroid disorders. The potential mechanisms underlying the observed correlations may involve the stimulatory effect of hCG on the thyroid gland in early pregnancy, the increased iodine requirements during pregnancy, and the physiological changes in thyroid hormone metabolism during pregnancy. Further studies are needed to investigate the causal relationship between iodine status and thyroid function during pregnancy and to identify the optimal iodine intake and supplementation strategies for pregnant women.

Data availability

All data generated or analyzed during this study are included in this published article.

References

  1. Yap YW, Onyekwelu E, Alam U. Thyroid disease in pregnancy. Clin Med (Lond). 2023;23(2):125–8. https://doi.org/10.7861/clinmed.2023-0018.

    Article  PubMed  Google Scholar 

  2. Parkes IL, Schenker JG, Shufaro Y. Thyroid disorders during pregnancy. Gynecol Endocrinol. 2012;28(12):993–8. https://doi.org/10.3109/09513590.2012.692001.

    Article  PubMed  CAS  Google Scholar 

  3. Fitzpatrick DL, Russell MA. Diagnosis and management of thyroid disease in pregnancy. Obstet Gynecol Clin North Am. 2010;37(2):173–93. https://doi.org/10.1016/j.ogc.2010.02.007.

    Article  PubMed  Google Scholar 

  4. Stagnaro-Green A. Thyroid antibodies and miscarriage: where are we at a generation later? J Thyroid Res. 2011;2011:841949. https://doi.org/10.4061/2011/841949.

    Article  PubMed  PubMed Central  Google Scholar 

  5. Casey BM, Dashe JS, Wells CE, et al. Subclinical hypothyroidism and pregnancy outcomes. Obstet Gynecol. 2005;105(2):239–45. https://doi.org/10.1097/01.AOG.0000152345.99421.22.

    Article  PubMed  Google Scholar 

  6. Haddow JE, Palomaki GE, Allan WC, et al. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med. 1999;341(8):549–55. https://doi.org/10.1056/NEJM199908193410801.

    Article  PubMed  CAS  Google Scholar 

  7. Zimmermann MB, Boelaert K. Iodine deficiency and thyroid disorders. Lancet Diabetes Endocrinol. 2015;3(4):286–95. https://doi.org/10.1016/S2213-8587(14)70225-6.

    Article  PubMed  CAS  Google Scholar 

  8. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014;10(3):136–42. https://doi.org/10.1038/nrendo.2013.251.

    Article  PubMed  CAS  Google Scholar 

  9. Delange F, Bürgi H, Chen ZP, Dunn JT. World status of monitoring iodine deficiency disorders control programs. Thyroid. 2002;12(10):915–24. https://doi.org/10.1089/105072502761016557.

    Article  PubMed  Google Scholar 

  10. König F, Andersson M, Hotz K, Aeberli I, Zimmermann MB. Ten repeat collections for urinary iodine from spot samples or 24-hour samples are needed to reliably estimate individual iodine status in women. J Nutr. 2011;141(11):2049–54. https://doi.org/10.3945/jn.111.144071.

    Article  PubMed  CAS  Google Scholar 

  11. Andersen S, Karmisholt J, Pedersen KM, Laurberg P. Reliability of studies of iodine intake and recommendations for number of samples in groups and in individuals. Br J Nutr. 2008;99(4):813–8. https://doi.org/10.1017/S0007114507842292.

    Article  PubMed  CAS  Google Scholar 

  12. Konrade I, Kalere I, Strele I, et al. Iodine deficiency during pregnancy: a national cross-sectional survey in Latvia. Public Health Nutr. 2015;18(16):2990–7. https://doi.org/10.1017/S1368980015000464.

    Article  PubMed  PubMed Central  Google Scholar 

  13. Bath SC, Steer CD, Golding J, Emmett P, Rayman MP. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of parents and children (ALSPAC). Lancet. 2013;382(9889):331–7. https://doi.org/10.1016/S0140-6736(13)60436-5.

    Article  PubMed  CAS  Google Scholar 

  14. Hynes KL, Otahal P, Hay I, Burgess JR. Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in the offspring: 9-year follow-up of the gestational iodine cohort. J Clin Endocrinol Metab. 2013;98(5):1954–62. https://doi.org/10.1210/jc.2012-4249.

    Article  PubMed  CAS  Google Scholar 

  15. Gowachirapant S, Jaiswal N, Melse-Boonstra A, et al. Effect of iodine supplementation in pregnant women on child neurodevelopment: a randomised, double-blind, placebo-controlled trial. Lancet Diabetes Endocrinol. 2017;5(11):853–63. https://doi.org/10.1016/S2213-8587(17)30332-7.

    Article  PubMed  CAS  Google Scholar 

  16. Glinoer D. The regulation of thyroid function during normal pregnancy: importance of the iodine nutrition status. Best Pract Res Clin Endocrinol Metab. 2004;18(2):133–52. https://doi.org/10.1016/j.beem.2004.03.001.

    Article  PubMed  CAS  Google Scholar 

  17. Hershman JM. The role of human chorionic gonadotropin as a thyroid stimulator in normal pregnancy. J Clin Endocrinol Metab. 2008;93(9):3305–6. https://doi.org/10.1210/jc.2008-1461.

    Article  PubMed  CAS  Google Scholar 

  18. Glinoer D. What happens to the normal thyroid during pregnancy? Thyroid. 1999;9(7):631–5. https://doi.org/10.1089/thy.1999.9.631.

    Article  PubMed  CAS  Google Scholar 

  19. Knudsen N, Bülow I, Laurberg P, Ovesen L, Perrild H, Jørgensen T. Association of tobacco smoking with goiter in a low-iodine-intake area. Arch Intern Med. 2002;162(4):439–43. https://doi.org/10.1001/archinte.162.4.439.

    Article  PubMed  Google Scholar 

  20. Laurberg P, Cerqueira C, Ovesen L, et al. Iodine intake as a determinant of thyroid disorders in populations. Best Pract Res Clin Endocrinol Metab. 2010;24(1):13–27. https://doi.org/10.1016/j.beem.2009.08.013.

    Article  PubMed  CAS  Google Scholar 

  21. Vanderpump MP, Tunbridge WM, French JM, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clin Endocrinol (Oxf). 1995;43(1):55–68. https://doi.org/10.1111/j.1365-2265.1995.tb01894.x.

    Article  PubMed  CAS  Google Scholar 

  22. Shrestha U, Gautam N, Agrawal KK, Jha AC, Jayan A. Iodine status among subclinical and overt hypothyroid patients by urinary iodine assay: a case-control study. Indian J Endocrinol Metab. 2017;21(5):719–23. https://doi.org/10.4103/ijem.IJEM_413_16.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  23. Thorpe-Beeston JG, Nicolaides KH, Felton CV, Butler J, McGregor AM. Maturation of the secretion of thyroid hormone and thyroid-stimulating hormone in the fetus. N Engl J Med. 1991;324(8):532–6. https://doi.org/10.1056/NEJM199102213240805.

    Article  PubMed  CAS  Google Scholar 

  24. Herrick KA, Perrine CG, Aoki Y, Caldwell KL. Iodine status and consumption of Key Iodine sources in the U.S. Population with Special attention to Reproductive Age women. Nutrients. 2018;10(7):874. https://doi.org/10.3390/nu10070874.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  25. Charlton KE, Gemming L, Yeatman H, Ma G. Suboptimal iodine status of Australian pregnant women reflects poor knowledge and practices related to iodine nutrition. Nutrition. 2010;26(10):963–8. https://doi.org/10.1016/j.nut.2009.08.016.

    Article  PubMed  Google Scholar 

  26. World Medical Association. World Medical Association Declaration of Helsinki: ethical principles for medical research involving human subjects. JAMA. 2013;310(20):2191–4. https://doi.org/10.1001/jama.2013.281053.

    Article  CAS  Google Scholar 

  27. International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). ICH Harmonised Tripartite Guideline: Guideline for Good Clinical Practice E6(R1). Geneva: ICH; 1996.

  28. Baloch Z, Carayon P, Conte-Devolx B, et al. Laboratory medicine practice guidelines. Laboratory support for the diagnosis and monitoring of thyroid disease. Thyroid. 2003;13(1):3–126. https://doi.org/10.1089/105072503321086962.

    Article  PubMed  Google Scholar 

  29. World Health Organization, United Nations Children’s Fund, International Council for Control of Iodine Deficiency Disorders. Assessment of iodine deficiency disorders and monitoring their elimination: a guide for programme managers. 3rd ed. Geneva: World Health Organization; 2007.

    Google Scholar 

  30. Bartels H, Böhmer M, Heierli C. Serum creatinine determination without protein precipitation. Clin Chim Acta. 1972;37:193–7. https://doi.org/10.1016/0009-8981(72)90432-9.

    Article  PubMed  CAS  Google Scholar 

  31. World Health Organization. Urinary iodine concentrations for determining iodine status in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization; 2013.

    Google Scholar 

  32. Shi X, Han C, Li C, et al. Optimal and safe upper limits of iodine intake for early pregnancy in iodine-sufficient regions: a cross-sectional study of 7190 pregnant women in China. J Clin Endocrinol Metab. 2015;100(4):1630–8. https://doi.org/10.1210/jc.2014-3704.

    Article  PubMed  CAS  Google Scholar 

  33. Rebagliato M, Murcia M, Espada M, et al. Iodine intake and maternal thyroid function during pregnancy. Epidemiology. 2010;21(1):62–9. https://doi.org/10.1097/EDE.0b013e3181c1592b.

    Article  PubMed  Google Scholar 

  34. Chen X, Wu C, Wang Z, et al. Iodine nutrition status and thyroid autoimmunity during pregnancy: a cross-sectional study of 4635 pregnant women. Nutr J. 2022;21(1):7. https://doi.org/10.1186/s12937-022-00760-6. Published 2022 Jan 29.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  35. Zimmermann MB, Connolly K, Bozo M, Bridson J, Rohner F, Grimci L. Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study. Am J Clin Nutr. 2006;83(1):108–14. https://doi.org/10.1093/ajcn/83.1.108.

    Article  PubMed  CAS  Google Scholar 

  36. Glinoer D, De Nayer P, Bourdoux P, et al. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab. 1990;71(2):276–87. https://doi.org/10.1210/jcem-71-2-276.

    Article  PubMed  CAS  Google Scholar 

  37. Liberman CS, Pino SC, Fang SL, Braverman LE, Emerson CH. Circulating iodide concentrations during and after pregnancy. J Clin Endocrinol Metab. 1998;83(10):3545–9. https://doi.org/10.1210/jcem.83.10.5163.

    Article  PubMed  CAS  Google Scholar 

  38. Glinoer D, De Nayer P, Delange F, et al. A randomized trial for the treatment of mild iodine deficiency during pregnancy: maternal and neonatal effects. J Clin Endocrinol Metab. 1995;80(1):258–69. https://doi.org/10.1210/jcem.80.1.7829623.

    Article  PubMed  CAS  Google Scholar 

  39. Li C, Guan H, Teng X, et al. An epidemiological study of the serum thyrotropin reference range and factors that influence serum thyrotropin levels in iodine sufficient areas of China. Endocr J. 2011;58(11):995–1002. https://doi.org/10.1507/endocrj.k11e-101.

    Article  PubMed  CAS  Google Scholar 

  40. Alexander EK, Pearce EN, Brent GA, et al. 2017 guidelines of the American thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the Postpartum. Thyroid. 2017;27(3):315–89. https://doi.org/10.1089/thy.2016.0457.

    Article  PubMed  Google Scholar 

  41. Farebrother J, Zimmermann MB, Andersson M. Excess iodine intake: sources, assessment, and effects on thyroid function. Ann N Y Acad Sci. 2019;1446(1):44–65. https://doi.org/10.1111/nyas.14041.

    Article  PubMed  CAS  Google Scholar 

  42. Thangaratinam S, Tan A, Knox E, Kilby MD, Franklyn J, Coomarasamy A. Association between thyroid autoantibodies and miscarriage and preterm birth: meta-analysis of evidence. BMJ. 2011;342:d2616. Published 2011 May 9. https://doi.org/10.1136/bmj.d2616

  43. Korevaar TIM, Muetzel R, Medici M, et al. Association of maternal thyroid function during early pregnancy with offspring IQ and brain morphology in childhood: a population-based prospective cohort study. Lancet Diabetes Endocrinol. 2016;4(1):35–43. https://doi.org/10.1016/S2213-8587(15)00327-7.

    Article  PubMed  CAS  Google Scholar 

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Acknowledgements

We would like to express our gratitude to all those who helped us during the writing of this manuscript.

Funding

A longitudinal study on the effect of iodine nutrition status on thyroid function in women of childbearing age during pregnancy and 6 weeks postpartum (Grant number 2022-2-2029).

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Author notes

  1. Xiao-Yan Guo and Yan Long contributed equally to this work.

Authors and Affiliations

  1. Department of Obstetrics and Gynecology, Beijing Friendship Hospital, Capital Medical University, No. 95 of Yong an Road, Xicheng District, Beijing, 100050, China

    Xiao-Yan Guo & Yan Long

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Guo XY and Long Y conceived of the study, participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.

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Correspondence to Yan Long.

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This study was conducted in accordance with the Declaration of Helsinki and approved by the ethics committee of Beijing Friendship Hospital (ethical batch number: BJFH-EC/2013-011). All patients signed an informed consent form for inclusion in the study.

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Not applicable.

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Guo, XY., Long, Y. The correlation between the thyroid function and urinary iodine/creatinine ratio of pregnant women attending a tertiary hospital in Beijing, China, during different trimesters. BMC Endocr Disord 24, 171 (2024). https://doi.org/10.1186/s12902-024-01704-3

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Keywords

BMC Endocrine Disorders

ISSN: 1472-6823

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