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

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 ...