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Sohn SY, Inoue K, Rhee CM, Leung AM. Risks of Iodine Excess. Endocr Rev 2024:bnae019. [PMID: 38870258 DOI: 10.1210/endrev/bnae019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 06/04/2024] [Accepted: 06/12/2024] [Indexed: 06/15/2024]
Abstract
Iodine is a micronutrient that is required for thyroid hormone synthesis. The iodide cycle in thyroid hormone synthesis consists of a series of transport, oxidation, organification, and binding/coupling steps in thyroid follicular cells. Common sources of iodine include the consumption of an iodine-rich diet or iodine fortified foods, the administration of amiodarone, iodine-containing supplements, or iodinated contrast media, and other miscellaneous sources. Methods to assess population iodine status include the measurement of urinary iodine concentrations, blood thyroglobulin levels, prevalence of elevated neonatal TSH levels, and thyroid volume. Although excessive iodine intake or exposure is generally well tolerated, an acute iodine load may result in thyroid dysfunction (hypothyroidism or hyperthyroidism) in certain susceptible individuals due to the failure to escape from the Wolff-Chaikoff effect and to the Jod-Basedow phenomenon, respectively. In this review, we discuss the associations between excessive iodine intake or exposure, with particular focus on iodinated contrast media as a common source of excess iodine in healthcare settings, and risks of incident thyroid dysfunction. We also summarize the risks of iodine excess in vulnerable populations and review current guidelines regarding the screening and monitoring of iodinated contrast-induced thyroid dysfunction. Finally, we discuss the long-term potential nonthyroidal health risks associated with iodine excess and suggest the need for more data to define safe upper limits for iodine intake, particularly in high-risk populations.
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Affiliation(s)
- Seo Young Sohn
- Division of Endocrinology, Department of Internal Medicine, Myongji Hospital, Hanyang University College of Medicine, Goyang, South Korea
| | - Kosuke Inoue
- Department of Social Epidemiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Hakubi Center, Kyoto University, Kyoto, Japan
| | - Connie M Rhee
- Division of Nephrology, Department of Medicine, Department of Medicine, University of California Los Angeles David Geffen School of Medicine, Los Angeles, California, USA
- Division of Nephrology, Department of Medicine, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
| | - Angela M Leung
- Division of Endocrinology, Diabetes, and Metabolism; Department of Medicine, University of California Los Angeles David Geffen School of Medicine, Los Angeles, California, USA
- Division of Endocrinology, Diabetes, and Metabolism; Department of Medicine, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
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Wang Z, Shao C, Zhu Y, Shi Z, Qu M, Song Q, Shen L, Mai S, Lu W, Sun Z, Xiang X, Zang J. Iodine Excess May Lead to Low Exam Score in Children Aged 8-10 Years. Biol Trace Elem Res 2024; 202:1468-1476. [PMID: 37500821 DOI: 10.1007/s12011-023-03783-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/15/2023] [Indexed: 07/29/2023]
Abstract
Recent research has shown that iodine excess may damage children's intelligence. Years of monitoring results in Shanghai show the iodine status has approached the upper limit of the appropriate range for children aged 8-10 years, indicating a risk of iodine excess. We used multi-stage random sampling to select children. Sixteen districts of Shanghai were divided into five units based on geographic location, and one primary school was randomly selected from each unit. In each selected school, about 40 children aged 8-10 years were randomly recruited to measure their urinary iodine concentration (UIC), household salt iodine concentration (SIC), the score of the final unified exam of the last semester, and school canteen salt iodine concentration. The median UIC of 3213 children aged 8-10 years in Shanghai was 195.4 (122.0, 285.8) µg/L and exceeded 200 µg/L in 48.8% of the population. Household and school canteen iodized salt coverage rates were 60.3% and 82.5% respectively, and mean household and school canteen SICs were 21.51 ± 9.30 mg/kg and 25.29 ± 3.40 mg/kg respectively. By correcting for potential confounding factors, logistic regression demonstrated that compared to the adequate iodine status group, students in the slight iodine excess group were less likely to get "A" (score > 90) in math, Chinese, and English exams (Math: OR = 0.775, 95% CI = 0.660-0.911, P = 0.002; Chinese: OR = 0.707, 95% CI = 0.543-0.842, P < 0.001; English: OR = 0.720, 95% CI = 0.610-0.849, P < 0.001). In Shanghai, the iodine status of 8-10-year-old children is approaching the upper limit of the adequate range. Iodine excess in Shanghai may lead to low exam scores for students.
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Affiliation(s)
- Zhengyuan Wang
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Chong Shao
- Department of Rheumatology and Immunology, Shanghai Tongren Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, 200050, China
| | - Yaoyan Zhu
- Baoshan Municipal Center for Disease Control and Prevention, Shanghai, 201900, China
| | - Zehuan Shi
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Mengying Qu
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Qi Song
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Liping Shen
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Shupeng Mai
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Wei Lu
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Zhuo Sun
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
| | - Xuesong Xiang
- Element Nutrition of National Health Commission, National Institute of Nutrition and Health, China CDC, Beijing, 100050, China.
| | - Jiajie Zang
- Shanghai Municipal Center for Disease Control and Prevention, Shanghai, 200336, China
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Cui Y, Wang Y, Zhang D, Duan Y, Li W, Li F, Chen L. How did we eliminate the hazards of water-borne excessive iodine in northern China? ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 269:115795. [PMID: 38091668 DOI: 10.1016/j.ecoenv.2023.115795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 11/24/2023] [Accepted: 12/05/2023] [Indexed: 01/12/2024]
Abstract
Drinking water is the main cause of iodine excess among Chinese residents and we have found that water iodine concentration (WIC) reduction was the effective intervening measure. In this study, to eliminate the hazards of water-borne excessive iodine, we firstly investigated the WIC of villages in Tianjin in 2017 to determine the distribution range. Secondly, the risk characterization of excessive iodine on residents in 6∼< 9 years old, 9∼< 12 years old, 12∼< 15 years old, 15∼< 18 years old and adults were evaluated, and the safe upper limit of WIC was determined. Finally, WIC was investigated again after the completion of WIC reduction in water-borne excessive-iodine villages in 2020, and the differences in urinary iodine concentration (UIC) and thyroid volume (Tvol) of children aged 8-10 years before and after WIC reduction were analyzed. The WIC of 2459 villages surveyed was 22.30 (8.60-58.80) μg/L and the maximum was 514 μg/L. There were 422 villages with WIC > 100 μg/L. Under the conditions of non-iodized salt intake, recommended amount of iodized salt intake and actual amount intake, the maximum of excessive iodine exposure hazard quotient (HQ) were the highest in the age group of 6∼< 9 years, which were 2.300, 2.663 and 2.771, the safe upper WIC limits were 223 μg/L, 142 μg/L and 118 μg/L and villages with HQ> 1 accounted for 4.14%, 6.09% and 6.88% of all villages, respectively. After the WIC reduction, the WIC of the former water-borne iodine-excess villages decreased to < 100 μg/L, and the UIC and Tvol of children decreased (both P < 0.001) and was within normal range. Determining the distribution range of water-borne iodine-excess areas, exploring appropriate intervening measure, carrying out risk assessment, determining the WIC safe upper limit, intervening and evaluating the intervention effect can be the process to eliminate the hazards of water-borne excessive iodine.
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Affiliation(s)
- Yushan Cui
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China.
| | - Yang Wang
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China
| | - Dandan Zhang
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China
| | - Yani Duan
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China
| | - Wenfeng Li
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China
| | - Fang Li
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China
| | - Lu Chen
- Tianjin Centers for Disease Control and Prevention, 6 Huayue Road, Hedong District, Tianjin 300011, China.
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Borjihan Q, Liang X, Chen T, Xiao D, Zhang Y, Wu H, Zhang Q, Dong A. Biological regulation on iodine using nano-starch for preventing thyroid dysfunction. JOURNAL OF HAZARDOUS MATERIALS 2023; 460:132200. [PMID: 37651936 DOI: 10.1016/j.jhazmat.2023.132200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 09/02/2023]
Abstract
The growing incidence of thyroid disease triggered by excess iodine uptake poses a severe health threat throughout the world. Extracellular interference therapies impede iodine transport across the sodium-iodide symporter (NIS) membrane protein and thus prevent excessive iodine uptake by thyroid cells, which may lessen the occurrence of disease. Herein, we for the first time utilized nano-starch particles (St NPs) to regulate iodine transport across the NIS protein of thyroid cells by using extracellular interference therapy. By precisely encapsulating iodine within the cavity of a glucan α-helix via hydrogen bonding, extracellular St NPs prevented excess iodine uptake by thyroid cells in vitro and in vivo; this down-regulated the expression of NIS protein (0.06-fold) and autophagy protein LC3B-II (0.35-fold). We also found that St NPs regulated the metabolic pathway of iodine in zebrafish. We believe this proposed strategy offers a novel insight into controlling iodine uptake by the thyroid and indicates a new direction for preventing iodine-induced thyroid disease.
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Affiliation(s)
- Qinggele Borjihan
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China
| | - Xuefang Liang
- College of Ecology and Environment, Inner Mongolia University, Hohhot 010021, PR China
| | - Ting Chen
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China
| | - Douxin Xiao
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China
| | - Yanling Zhang
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China
| | - Haixia Wu
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China.
| | - Qing Zhang
- College of Chemistry, Tangshan Normal University, Tangshan 063000, PR China.
| | - Alideertu Dong
- College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, PR China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, Hohhot 010021, PR China.
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Wu W, Chen Y, Guo W, Zhang K, Chen W, Fu M, Pan Z, Yang Y, Zhang N, Zhang W. The Relationship Between Iodine Excess and Thyroid Function During Pregnancy and Infantile Neurodevelopment at 18-24 Months. J Nutr 2023; 153:2320-2327. [PMID: 37182695 DOI: 10.1016/j.tjnut.2023.05.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 04/15/2023] [Accepted: 05/10/2023] [Indexed: 05/16/2023] Open
Abstract
BACKGROUND Thyroid disease is a prevalent condition during pregnancy, and excessive iodine intake can lead to changes in thyroid function. However, research on the relationship between maternal iodine excess, thyroid hormones during pregnancy, and infantile neurodevelopment is limited. OBJECTIVES This study aimed to explore the relationship between maternal iodine excess and thyroid hormones during pregnancy and infantile neurodevelopment. The objective was to provide evidence to support and enhance the prevention of neurodevelopmental retardation in infants. METHODS From 2016 to 2018, a prospective study was conducted from pregnancy to 18-24 mo postpartum. Maternal urinary iodine concentration (UIC), thyroid-stimulating hormone (TSH), total serum iodine (TSI), and nonprotein-bound serum iodine during pregnancy were determined. The Gesell Development Scale was used to assess neurodevelopment of infants aged 18-24 mo. The iodine status of pregnant females was divided into following 4 groups on the basis of the distribution of maternal UIC: <100 μg/L (moderate deficiency), 100-149 μg/L (mild deficiency), 150-249 μg/L (sufficiency), and >250 μg/L (above requirement). RESULTS Our study included 469 mother-infant pairs. Compared with the maternal UIC of 150-249 μg/L during pregnancy, risk of adaptive developmental delay was increased in infants with maternal UIC ≥250 μg/L (OR: 2.38; 95% CI: 1.06, 5.35). Pregnant females with TSI >90th quantiles were more likely to have offspring with language developmental delay than those with lower TSI in 10th-90th quantiles (OR: 3.06; 95% CI: 1.09, 8.58). Risk of fine motor developmental delay was increased in infants with maternal TSH ≥2.5 mIU/L during pregnancy (OR: 4.32; 95% CI: 1.43, 13.0). CONCLUSIONS Maternal iodine nutritional status above requirement (UIC ≥250 μg/L or TSI >90th quantiles) during pregnancy negatively affects infantile neurodevelopment. Maternal TSH ≥2.5 mIU/L during pregnancy was an independent risk factor for infantile neurodevelopment. This trial was registered at clinicaltrials.gov as NCT03710148.
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Affiliation(s)
- Wen Wu
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Yanting Chen
- Department of Epidemiology and Biostatistics, School of Public Health, Guangdong Medical University, Guangdong, China
| | - Wenxing Guo
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Kexin Zhang
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Wen Chen
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Min Fu
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Ziyun Pan
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Ying Yang
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Naifan Zhang
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China
| | - Wanqi Zhang
- Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China; Tianjin Key Laboratory of Environment, Nutrition and Public Health, Center for International Collaborative Research on Environment, School of Public Health, Tianjin Medical University, Tianjin, China; Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.
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Jin M, Zhou Z, Zhang L, Chen Y, Liu L, Shen H. Effects of Excessive Iodine on the BDNF-TrkB Signaling Pathway and Related Genes in Offspring of EAT Rats. Biol Trace Elem Res 2023; 201:776-785. [PMID: 35322353 DOI: 10.1007/s12011-022-03187-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Accepted: 02/28/2022] [Indexed: 01/21/2023]
Abstract
Excess iodine can cause autoimmune thyroiditis (AIT) in women, but it is unclear whether this has any implications for neurodevelopmental mechanisms in offspring. We studied the effects of experimental autoimmune thyroiditis (EAT) rats with different amounts of iodine intake on offspring brain development via the brain-derived neurotrophic factor (BDNF)-tropomycin receptor kinase B (TrkB) signaling pathway, because BDNF plays an important role in neurodevelopment. Rats in three thyroglobulin (Tg) immunized groups with varying iodine intakes (Tg (100 µg/L iodine), Tg + High-iodine I group (Tg + HI, 20 mg/L iodine), and Tg + High-iodine II group (Tg + HII, 200 mg/L iodine)) were injected with 800 µg Tg once every 2 weeks for 3 times. Rats in the control group (NI, 100 µg/L iodine) were immunized with saline. Arsenic-cerium catalytic spectrophotometry was used to measure urine iodine levels. The lymphocytic infiltration in the thyroids was observed by histopathological studies. Thyroid autoantibodies levels were measured using radioimmunoassay. The norepinephrine (NE) contents were measured by an enzyme-linked immunosorbent assay. The levels of the BDNF-TrkB signaling pathway and related genes were measured by quantitative real-time PCR and Western blot. Urinary iodine levels increased as iodine intake increased. Lymphocytes were significantly aggravated in Tg-immunized rats. Serum thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb) levels were clearly elevated in Tg-immunized rats. Tg-immune groups had significantly lower NE levels. The BDNF-TrkB signaling pathway and related gene mRNA and protein levels were found to be significantly lower in Tg-immune groups with higher iodine levels. Maternal AIT may reduce the levels of certain neurodevelopmental mechanisms in the offspring, such as the BDNF-TrkB signaling pathway and related factors, while excessive iodine consumption by the mother may exacerbate this effect.
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Affiliation(s)
- Meihui Jin
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China
| | - Zheng Zhou
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China
| | - Li Zhang
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China
| | - Yao Chen
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China
| | - Lixiang Liu
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China.
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China.
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China.
| | - Hongmei Shen
- Centre for Endemic Disease Control, Chinese Centre for Disease Control and Prevention, Harbin Medical University, Harbin City, Heilongjiang Province, 150081, People's Republic of China.
- National Health Commission & Education Bureau of Heilongjiang Province, Key Laboratory of Etiology and Epidemiology, Harbin Medical University (23618504), Harbin, China.
- Heilongjiang Provincial Key Laboratory of Trace Elements and Human Health, Harbin Medical University, Harbin, China.
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Association between Elevated Iodine Intake and IQ among School Children in Portugal. Nutrients 2022; 14:nu14214493. [PMID: 36364754 PMCID: PMC9657725 DOI: 10.3390/nu14214493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Revised: 10/05/2022] [Accepted: 10/18/2022] [Indexed: 11/23/2022] Open
Abstract
The goal of this work was to examine whether elevated iodine intake was associated with adverse effects on IQ among school-age children in Portugal. In a representative sample of children from the north of the country, IQ percentiles by age (assessed with Raven’s Colored Progressive Matrices) were dichotomized to <50 (“below-average” IQs) and ≥50. Morning urine iodine concentrations, corrected for creatinine, were dichotomized to <250 µg/g and ≥250 µg/g, according to the European Commission/Scientific Committee on Food’s tolerable upper level of daily iodine intake for young children. Data were examined with Chi-square tests, logistic regression, and GLM univariate analysis. The sample (N = 1965) was classified as generally iodine-adequate (median urinary iodine concentration = 129 µg/L; median iodine-to-creatinine ratio = 126 µg/g) according to the WHO’s criteria. A greater proportion of children in the ≥250 µg/g group had below-average IQs, compared to children with less than 250 µg/g (p = 0.037), despite a sizable (though non-significant) proportion of children in the less-than-250 µg/g group also presenting below-average IQs, at the bottom of the iodine distribution (<50 µg/g). The proportion of below-average IQs increased with increasingly elevated iodine concentrations (p = 0.047). The association remained significant after the adjustment for confounders, with the elevated iodine group showing increased odds of having below-average IQs when compared with the non-elevated iodine group (OR 1.55; 95% CI 1.11−2.17; p = 0.011). Consistently, the former group presented a lower mean IQ than the latter (p = 0.006). High iodine intake was associated with lower IQs even in a population classified as iodine-adequate. These results bear on child cognition and on initiatives involving iodine supplementation.
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Goodman CV, Hall M, Green R, Chevrier J, Ayotte P, Martinez-Mier EA, McGuckin T, Krzeczkowski J, Flora D, Hornung R, Lanphear B, Till C. Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence. Nutrients 2022; 14:2920. [PMID: 35889877 PMCID: PMC9319869 DOI: 10.3390/nu14142920] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 12/07/2022] Open
Abstract
In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.
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Affiliation(s)
- Carly V. Goodman
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - Meaghan Hall
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - Rivka Green
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - Jonathan Chevrier
- Department of Epidemiology, Biostatistics, and Occupational Health, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC H3A 1G1, Canada;
| | - Pierre Ayotte
- Département de Médecine Sociale et Préventive, Faculté de Médecine, Université Laval, Québec, QC G1V 0A6, Canada;
| | - Esperanza Angeles Martinez-Mier
- Cariology, Operative Dentistry and Dental Public Health, Indiana University School of Dentistry, Indianapolis, IN 46202, USA;
| | - Taylor McGuckin
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - John Krzeczkowski
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - David Flora
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
| | - Richard Hornung
- Pediatrics and Environmental Health, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA;
| | - Bruce Lanphear
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada;
| | - Christine Till
- Department of Psychology, York University, Toronto, ONT M3J 1P3, Canada; (C.V.G.); (M.H.); (R.G.); (T.M.); (J.K.); (D.F.)
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