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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.
Thyroid. 2018 06; 28(6):773-779.T

Abstract

BACKGROUND

Iodine is an important element for the synthesis of thyroid hormone, and its deficiency or excessive intake is associated with various thyroid diseases. Little is known about the association between iodine status and thyroid function among children and adolescents living in iodine-rich areas. Therefore, this study analyzed this association using data from a nationwide survey.

METHODS

From the Korea National Health and Nutrition Examination Surveys VI (2013-2015) data, 1288 subjects (711 male) aged 6-19 years who underwent a urinary iodine concentration (UIC) test and 1000 subjects (564 male) aged 10-19 years who underwent a thyroid function test were included in this study. Serum levels of thyrotropin (TSH), free thyroxine (fT4), and thyroperoxidase antibodies (TPOAb) were analyzed. Subclinical hypothyroidism (SCH) was defined as TSH >5.5 μIU/mL with a normal fT4 level. Median daily iodine intake was calculated from the UIC. Daily sodium intake was derived from the nutritional survey data of 1181 subjects.

RESULTS

The median UIC was 449 μg/L (range 15-21,905 μg/L), and the prevalence rates of UIC ≥300 μg/L and ≥1000 μg/L were 64.9% and 25.0%, respectively. The prevalence rates of a sodium intake >2000 mg/day and iodine intake >2400 μg/day were 75.0% (885/1181) and 12.7% (164/1288), respectively. The prevalence rates of SCH and TPOAb >34 IU/mL were 7.2% (72/1000) and 2.3% (23/1000), respectively. The prevalence of SCH was significantly higher in the iodine deficient and iodine excess groups compared to those in the UIC 100-299.9 μg/L group (p = 0.038). Therefore, there was a U-shaped and inverted U-shaped correlation between serum levels of TSH and fT4 with UIC, respectively. These correlations were especially prominent when UIC was >1000 μg/L. There was no definite correlation between TPOAb and UIC.

CONCLUSIONS

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.

Authors+Show Affiliations

1 Department of Pediatrics, Hallym University Sacred Heart Hospital , Anyang, Korea.2 Department of Pediatrics, Kangdong Sacred Heart Hospital , Seoul, Korea.3 Department of Pediatrics, Seoul National University Bundang Hospital , Seongnam, Korea.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

29737233

Citation

Kang, Min Jae, et al. "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." Thyroid : Official Journal of the American Thyroid Association, vol. 28, no. 6, 2018, pp. 773-779.
Kang MJ, Hwang IT, Chung HR. 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. Thyroid. 2018;28(6):773-779.
Kang, M. J., Hwang, I. T., & Chung, H. R. (2018). 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. Thyroid : Official Journal of the American Thyroid Association, 28(6), 773-779. https://doi.org/10.1089/thy.2017.0507
Kang MJ, Hwang IT, Chung HR. 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. Thyroid. 2018;28(6):773-779. PubMed PMID: 29737233.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - 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. AU - Kang,Min Jae, AU - Hwang,Il Tae, AU - Chung,Hye Rim, PY - 2018/5/9/pubmed PY - 2019/5/10/medline PY - 2018/5/9/entrez KW - hypothyroidism KW - thyroid function KW - urinary iodine SP - 773 EP - 779 JF - Thyroid : official journal of the American Thyroid Association JO - Thyroid VL - 28 IS - 6 N2 - BACKGROUND: Iodine is an important element for the synthesis of thyroid hormone, and its deficiency or excessive intake is associated with various thyroid diseases. Little is known about the association between iodine status and thyroid function among children and adolescents living in iodine-rich areas. Therefore, this study analyzed this association using data from a nationwide survey. METHODS: From the Korea National Health and Nutrition Examination Surveys VI (2013-2015) data, 1288 subjects (711 male) aged 6-19 years who underwent a urinary iodine concentration (UIC) test and 1000 subjects (564 male) aged 10-19 years who underwent a thyroid function test were included in this study. Serum levels of thyrotropin (TSH), free thyroxine (fT4), and thyroperoxidase antibodies (TPOAb) were analyzed. Subclinical hypothyroidism (SCH) was defined as TSH >5.5 μIU/mL with a normal fT4 level. Median daily iodine intake was calculated from the UIC. Daily sodium intake was derived from the nutritional survey data of 1181 subjects. RESULTS: The median UIC was 449 μg/L (range 15-21,905 μg/L), and the prevalence rates of UIC ≥300 μg/L and ≥1000 μg/L were 64.9% and 25.0%, respectively. The prevalence rates of a sodium intake >2000 mg/day and iodine intake >2400 μg/day were 75.0% (885/1181) and 12.7% (164/1288), respectively. The prevalence rates of SCH and TPOAb >34 IU/mL were 7.2% (72/1000) and 2.3% (23/1000), respectively. The prevalence of SCH was significantly higher in the iodine deficient and iodine excess groups compared to those in the UIC 100-299.9 μg/L group (p = 0.038). Therefore, there was a U-shaped and inverted U-shaped correlation between serum levels of TSH and fT4 with UIC, respectively. These correlations were especially prominent when UIC was >1000 μg/L. There was no definite correlation between TPOAb and UIC. CONCLUSIONS: 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. SN - 1557-9077 UR - https://www.unboundmedicine.com/medline/citation/29737233/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_ L2 - https://www.liebertpub.com/doi/full/10.1089/thy.2017.0507?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -