Urinary Iodine and Selenium Intake as Risk Factors for Thyroid Autoimmune Disease

by | Jan 2, 2025 | 2024, Autoimmune Disease, Iodine, Minerals, Recent Articles, Selenium, Thyroid

Written by Chrystal Moulton, Science Writer. Urinary iodine concentration between 500-800 mcg/l is significantly associated with the risk of developing thyroid autoimmunity, thyroid peroxidase antibody positivity, and thyroglobulin antibody positivity.

thyroid healthPrevious studies have shown that iodine deficiency is a risk factor of thyroid autoimmunity1,2. Studies have also shown that selenium is essential for thyroid health3. One animal study demonstrated that rats fed high iodine diets but were selenium deficient developed thyroid fibrosis, which was subsequently resolved by selenium supplementation4. Other studies have demonstrated that, due to its antioxidant capabilities, selenium supplementation can prevent or delay beyond onset of Hashimoto’s thyroiditis5,6. Therefore, striking the right balance between iodine and selenium could have a protective effect against the development of thyroid diseases. In the current study, researchers used data from the National Health and Nutrition Examination Survey [NHANES] to assess the relationship between urinary iodine concentration, thyroid antibody positivity, and selenium intake7.

Researchers utilized data Between 2007 and 2012 that included thyroid function tests, urinary iodine concentration, as well as complete examination and questionnaire data. Data from participants who were ≥ 20 years old with urinary iodine concentration (UIC) ≤ 800 mcg/l, who were not pregnant and had complete thyroid function data were included for this analysis. Dietary recall data was used to calculate selenium intake, which also included selenium supplementation with daily vitamins or the like. Participants were characterized into three groups based on selenium intake with tertile 1 being the lowest and tertile 3 being the highest intake group. Thyroid function antibodies were measured through blood samples taken from each participant. Urine samples are also taken to calculate urinary iodine concentration (UIC). Researchers utilized logistical regression analysis to determine whether there was any relationship between urinary iodine concentration (UIC) and the presence of thyroid antibodies. Regression analysis is also used to determine whether selenium intake had any effect on the relationship between urinary iodine concentration (UIC) and thyroid antibody positivity.

Data from 6612 participants were included in this analysis. Participants were stratified into 5 groups based on UIC. At baseline, selenium intake (P <0.01), BMI (P = 0.001), sex (P <0.001), smoking status (P = 0.002), thyroglobulin antibody positivity (P = 0.029), and household income (P = 0.009) were significantly different between the five groups. Researchers saw a significantly increased risk of both thyroid peroxidase antibody positivity (OR = 1.57, P = 0.022) and thyroglobulin antibody positivity (OR = 2.00, P = 0.025) among individuals with UIC between 500 – 800 mcg/l, even after adjusting for all confounding variables. There was also a significant risk of thyroid autoimmunity among individuals in this same group after adjusting for all confounding factors (OR = 1.62, P = 0.024). Researchers also observed a significant nonlinear relationship between UIC and thyroglobulin antibody positivity (P-nonlinear <0.05). Based on the nonlinear curve, thyroglobulin antibody positivity increased significantly when UIC is >261.59 mcg/l. When taking selenium intake into account, researchers also observed a significant nonlinear relationship between selenium intake and thyroglobulin antibody positivity (P- nonlinear = 0.013). Researchers also observed a significant nonlinear relationship between thyroglobulin antibody positivity and UIC among individuals stratified based on selenium intake. Individuals in the intermediate selenium group [tertile 2] had a significantly increased the risk of thyroid globulin antibody positivity when UIC is >266.22 mcg/l (P- nonlinear = 0.0001); While individuals at the lowest intake of selenium had an increased risk of thyroglobulin antibody positivity when UIC is >261.59 mcg/l (P-nonlinear = 0.0431). A significant nonlinear relationship was also observed in the intermediate selenium group for thyroid peroxidase antibody positivity (P- nonlinear = 0.0003) with an increased risk of thyroid peroxidase antibody positivity when UIC is >121.47 mcg/l. Regression analysis showed that after adjusting for all confounding factors, individuals in the lowest selenium intake group with a UIC between 200-300 mcg/l was 1.91 times more likely to have thyroid peroxidase antibody positivity (OR = 1.91, P = 0.046). Also, individuals in the intermediate selenium intake group with the UIC between 300-500 mcg/l (OR = 1.82, P = 0.019) and between 500-800 mcg/l (OR = 2.6, P = 0.002) had a significantly increased risk of thyroid peroxidase antibody positivity. No significant interaction was observed in the high selenium intake group and no further interactions were observed for thyroglobulin antibody positivity and thyroid autoimmunity among the selenium stratified groups.

Results from this analysis showed that UIC between 500-800 mcg/l is significantly associated with the risk of developing thyroid autoimmunity, thyroid peroxidase antibody positivity, and thyroglobulin antibody positivity. Researchers also found that moderate intake of selenium with a UIC between 300-800 mcg/l is significantly associated with an increase the risk of thyroid peroxidase antibody positivity. Additional studies will be needed to investigate the intakes of selenium and iodine which could delay or prevent thyroid autoimmune diseases.

Source: Zhang, Chenyu, Haoyu Wang, Weiping Teng, and Zhongyan Shan. “The Relationships among the Urinary Iodine Concentration, Selenium Intake, and Thyroid Antibodies in Adults, Including the Interaction between Iodine and Selenium: National Health and Nutrition Examination Survey 2007–2012.” Nutrients 16, no. 20 (2024): 3443.

© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/
4.0/).

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Posted January 2, 2025.

Chrystal Moulton BA, PMP, is a 2008 graduate of the University of Illinois at Chicago. She graduated with a bachelor’s in psychology with a focus on premedical studies and is a licensed project manager. She currently resides in Indianapolis, IN.

References:

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