Endocrinol Metab.  2021 Jun;36(3):607-618. 10.3803/EnM.2021.1005.

Evaluation of Iodine Status among Korean Patients with Papillary Thyroid Cancer Using Dietary and Urinary Iodine

• Choi JY
• Lee JH
• Song Y

• KMID: 2517651
• DOI: http://doi.org/10.3803/EnM.2021.1005

Abstract

Background
Concerns have been raised regarding thyroid disorders caused by excessive iodine in Koreans, who have iodine-rich diets. This study evaluated iodine status using dietary iodine intake and urinary iodine in papillary thyroid cancer (PTC) patients.
Methods
Dietary data of PTC patients were assessed using a 24-hour recall and food frequency questionnaire (FFQ), and urinary iodine concentrations (UICs) were also obtained. To compare the iodine status of PTC patients, Korean adults with or without thyroid disease from the Korea National Health and Nutrition Examination Survey, which had 24-hour recall data and urinary iodine measurements, were analyzed.
Results
The median daily iodine intake by 24-hour recall was 341.7 μg/day in PTC patients, similar to the levels of other Korean adults. Based on UICs, the prevalence of excessive iodine was 54.4% in PTC patients, which was similar to the prevalence among subjects with thyroid disease (55.4%) but slightly higher than that in subjects without thyroid disease (47.7%). Based on dietary iodine by 24-hour recall, the prevalence of excessive iodine intake was 7.2%, which was higher than that among subjects with (4.4%) or without (3.9%) thyroid disease. The dietary iodine intake based on 24-hour recall was closely correlated with the UIC (r=0.4826) in PTC patients, but dietary iodine by FFQ was not significantly correlated with either 24-hour recall or UIC-based dietary iodine.
Conclusion
Excessive iodine intake was more common in PTC patients than in subjects without thyroid disease. Further longitudinal research is necessary to elucidate the role of dietary iodine in PTC.

Keyword

Thyroid cancer; papillary; Thyroid diseases; Iodine; Dietary intake

Figure

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  Fig. 1 Flowchart of subject selection process to evaluate iodine status using data from the Gachon University Gil Medical Center and the 2013–2015 Korea National Health and Nutrition Examination Survey (KNHANES). FFQ, food frequency questionnaire; BMI, body mass index.

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  Fig. 2 Distribution of urinary iodine concentrations according to thyroid disease groups in Korean adults. (A) The percentage of subjects by World Health Recommendations and (B) by further categories among subjects with excessive urinary iodine (>300 μg/L). WHO, World Health Organization.

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  Fig. 3 Distribution of dietary iodine and evaluation of excessive iodine intake by dietary reference intakes for Koreans according to thyroid disease groups in Korean adults. (A) The distribution of dietary iodine intake and (B) the percentage of subjects who consumed less than the estimated average requirement (EAR) or more than the tolerable upper intake level (UL) of iodine. Q1: 25th percentile, Q3: 75th percentile, P90: 90th percentile, box: Q3-Q1 (interquartile range), ⋄: mean.

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  Fig. 4 The contribution of major food groups to total iodine intake based on 24-hour recall among subjects according to thyroid disease groups.

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  Fig. 5 Dietary iodine intake and the major food items contributing to total iodine intake by different dietary assessment methods in patients with papillary thyroid cancer. aBox and whisker plot; Q1: 25th percentile, Q3: 75th percentile, P90: 90th percentile, box: Q3-Q1 (interquartile range), ⋄: mean.

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