Excessive Iodine Intake and Subclinical Hypothyroidism in Children and Adolescents Aged 6–19 Years: Results of the Sixth Korean National Health and Nutrition Examination Survey, 2013–2015

Kang, Min Jae; Hwang, Il Tae; Chung, Hye Rim

doi:10.1089/thy.2017.0507

Cited by 35 publications

(36 citation statements)

References 28 publications

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“…Although UIC was statistically associated with levels of TSH and fT4 in the present study, no association was found between iodine status and incidence of thyroid dysfunction. Nevertheless, in a study performed by Kang et al [29] on children and adolescents, iodine excess was found to be associated with subclinical hypothyroidism. Iodine excess has also been reported to be associated with iodine-induced thyroid dysfunction and autoimmune thyroid diseases [30].…”

Section: Discussionmentioning

confidence: 97%

Iodine status and characteristics of Korean adolescents and their parents based on urinary iodine concentration: a nationwide cross-sectional study

Choi

Cheong

Chueh

et al. 2019

Ann Pediatr Endocrinol Metab

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Purpose Iodine is a major component of thyroid hormones. Both deficiency and excess of iodine are major risk factors for thyroid disease, making it important to accurately assess iodine level in the human body. Urinary iodine concentration (UIC) is a commonly used measure of iodine status. However, there is little research on iodine status and related characteristics in Korean adolescents. Methods Using data from the sixth Korea National Health and Nutrition Examination Survey (KNHANES VI) for the years 2013–2015, we analyzed UIC and thyroid function test results in adolescents aged 10–18 years and their parents. We also investigated the influence of socioeconomic factors and family history of thyroid disease on iodine status. Results Mean UIC in Korean adolescents was 963.5±55.7 μg/L. Among evaluated subjects, 6.6%±1.0%, 29.8%±1.7%, and 63.9%±1.9% had low (UIC<100 μg/L), adequate (UIC: 100–299.9 μg/L), and excess (UIC≥300 μg/L) iodine concentrations, respectively. Based on regional trends, the incidence of iodine deficiency exceeded 10% in several regions, even though there was a dominance of regions with excess iodine. Parental UIC, female sex, average monthly income, and expenditure were all found to affect the iodine status of Korean adolescents. Conclusions Although regional differences exist, the iodine status in Korean adolescents is mainly affected by the eating habits of their families and socioeconomic factors. Therefore, monitoring of iodine status is necessary in this population.

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Section: Discussionmentioning

confidence: 97%

Iodine status and characteristics of Korean adolescents and their parents based on urinary iodine concentration: a nationwide cross-sectional study

Choi

Cheong

Chueh

et al. 2019

Ann Pediatr Endocrinol Metab

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“…World Health Organization (WHO) suggests that an adequate UIC should be between 100 and 200 μg/L, and an UIC in the range of 200-299 μg/L and >300 μg/L indicate more than adequate intake and the presence of excessive iodine, respectively (21). According to the criteria of iodine status above, there are a large percentage of persons with either iodine deficiency or excessive iodine (28,48,49). It has been clear that iodine deficiency can result in impaired production of thyroid hormones and thus cause adverse effects on human health.…”

Section: Discussionmentioning

confidence: 99%

“…After excluding studies that did not fulfill the inclusion criteria, 185 candidate studies were further evaluated by reading full texts. Another 164 studies were further excluded and 21 studies from literature were eligible into meta-analysis (26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46). Therefore, a total of 22 studies (21 studies from literature and our cross-sectional study) were finally included.…”

Section: Dose-response Meta-analysismentioning

confidence: 99%

U-shaped relationship between iodine status and thyroid autoimmunity risk in adults

Wang

et al. 2019

European Journal of Endocrinology

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Background Iodine status has long been regarded as an environmental determinant for thyroid dysfunction, but its relationship with thyroid autoimmunity (TAI) is still controversial. Our study aimed to elucidate the relationship between iodine status and TAI through both a population-based study and a dose–response meta-analysis of eligible epidemiological studies. Methods A population-based, cross-sectional study was firstly carried out, which enrolled a total of 2808 Chinese adults. Odds ratio (OR) with 95% confidence interval (95% CI) was calculated through logistic regression analysis. A dose–response meta-analysis of eligible epidemiological studies was also carried out. Results The cross-sectional study showed an U-shaped relationship between iodine intake and TAI in adults. Compared with those with more than adequate iodine status, individuals with iodine deficiency, adequate iodine status and iodine excess all had higher risk of TAI, and the adjusted ORs were 1.50 (95% CI 1.03–2.17, P = 0.032), 1.50 (95% CI 1.09–2.07, P = 0.013) and 1.68 (95% CI 1.11–2.53, P = 0.014), respectively. The dose–response meta-analysis included 22 epidemiological studies with a total of 69,987 participants and further validated the U-shaped relationship between iodine intake and TAI in adults, which proved the significantly increased risk of TAI among individuals with either iodine deficiency or iodine excess. Stratified analysis of studies with low risk of confounding bias also identified similar findings. Conclusion The study suggests an U-shaped relationship between iodine intake and TAI in adults, and both iodine deficiency and iodine excess are risk factors of TAI in adults. The underlying mechanisms need to be elucidated in future studies.

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“…Excess iodine intakes in populations can result from diets that are naturally high in iodine and/or groundwater. In South Korea, the mUIC in SAC and adolescents is 449 µg/L, mainly due to high intakes of iodine-rich seaweed (25). Djibouti, on the Horn of Africa, has excess iodine intakes due to very high iodine in groundwater: the median iodine concentration in drinking water is 92 μg/L (IQR:37-158 μg/L) and the mUIC is 335 μg/L in SAC and 265 μg/L in pregnant women, despite only 1.6% of Djibouti salt samples being adequately iodized (>15 ppm) (26).…”

Section: Countries With Excessive Iodine Intakementioning

confidence: 99%

GLOBAL ENDOCRINOLOGY: Global perspectives in endocrinology: coverage of iodized salt programs and iodine status in 2020

Zimmermann

Andersson

2021

European Journal of Endocrinology

126

102

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Iodine deficiency has multiple adverse effects on growth and development. Diets in many countries cannot provide adequate iodine without iodine fortification of salt. In 2020, 124 countries have legislation for mandatory salt iodization and 21 have legislation allowing voluntary iodization; as a result, 88% of the global population uses iodized salt. For population surveys, the urinary iodine concentration (UIC) should be measured and expressed as the median, in μg/L. The quality of available survey data is high: UIC surveys have been done in 152 out of 194 countries in the past 15 years; in 132 countries the studies were nationally representative. The number of countries with adequate iodine intake has nearly doubled from 67 in 2003 to 118 in 2020. However, 21 countries remain deficient, while 13 countries have excessive intakes, either due to excess groundwater iodine, or over-iodized salt. Iodine programs are reaching the poorest of the poor: of the 15 poorest countries in the world, 10 are iodine sufficient and only three (Burundi, Mozambique and Madagascar) remain mild-to-moderately deficient. Nigeria and India have unstable food systems and millions of malnourished children, but both are iodine sufficient and population coverage with iodized salt is a remarkable 93% in both. Once entrenched, iodine programs are often surprisingly durable even during national crises; for example, war-torn Afghanistan and Yemen are iodine sufficient. However, equity of iodized salt programs within countries remains an important issue. In summary, continued support of iodine programs is needed to sustain these remarkable global achievements, and to reach the remaining iodine-deficient countries.

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Excessive Iodine Intake and Subclinical Hypothyroidism in Children and Adolescents Aged 6–19 Years: Results of the Sixth Korean National Health and Nutrition Examination Survey, 2013–2015

Abstract: Excess iodine was prevalent in Korean children and adolescents, and it may be associated with SCH. Therefore, monitoring the iodine status and education on adequate intake are needed in iodine-rich areas.

Cited by 35 publications

References 28 publications

Iodine status and characteristics of Korean adolescents and their parents based on urinary iodine concentration: a nationwide cross-sectional study

Iodine status and characteristics of Korean adolescents and their parents based on urinary iodine concentration: a nationwide cross-sectional study

U-shaped relationship between iodine status and thyroid autoimmunity risk in adults

GLOBAL ENDOCRINOLOGY: Global perspectives in endocrinology: coverage of iodized salt programs and iodine status in 2020

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