Impact of iodine nutrition status on thyroid autoimmunity in subclinical hypothyroid patients attending a tertiary hospital of Bangladesh

Md Asaduzzaman, A B M Kamrul-Hasan, A K M Aminul-Islam, Md Rafiq-Uddin, MA Hasanat, Md Fariduddin

Thyroid Research and Practice 2018 15(2):75-79

Background: Iodine excess may trigger thyroid autoimmunity. The aim of this study was to observe the iodine nutrition status in thyroid autoantibody-positive and -negative subclinical hypothyroid (SCH) patients. Materials and Methods: This cross-sectional study enrolled 99 SCH patients (50 thyroid autoantibody-positive and 49 autoantibody-negative) aging 18–65 years from June 2014 to April 2015. Serum free thyroxine (FT4), thyroid stimulating hormone (TSH), anti-thyroid peroxidase (TPO), and anti-thyroglobulin (TG) antibodies were measured; the urinary iodine concentration (UIC) was estimated and the iodine nutrition status was categorized (deficiency, optimal, more than optimal, and excessive) according to urinary iodine levels by WHO/UNICEF/ICCIDD recommended cutoffs. Statistical analysis was performed by using IBM SPSS Statistics for Windows, version 23.0 software. P ≤≤0.05 was considered to be statistically significant. Results: The antibody-positive SCH subjects had a higher mean (299.03 ± 19.43 vs. 263.54 ± 23.10, mean ± standard error of mean, P = 0.314) and median (295.85 vs. 212.70, P = 0.035) UIC than antibody-negative ones. Although there was no statistical difference in the frequency of antibody-positive and antibody-negative status among various subgroups of iodine status (χ2 = 4.941, P = 0.176); the anti-TG titer showed significant statistical difference among the subgroups (P = 0.047) and was the highest in patients having excessive iodine. The frequency of goiter was also higher in patients having over sufficient (more than optimal and excessive) UIC (P = 0.905). UIC did not significantly correlate with serum TSH, FT4 levels, and anti-TPO titer but had a significant positive correlation with anti-TG titer (r = 0.292, P = 0.003). Conclusion: Over sufficient state of UI may be related to the thyroid autoimmunity and goiter in SCH patients.

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