title: Correlation between iodine intake and thyroid function in subjects with normal thyroid function.
abstract: Excessive iodine intake is known to induce hypothyroidism in people who have underlying thyroid disorders. However, few studies have been performed on subjects with normal thyroid function without a history of autoimmune thyroid disease. We hypothesized that high iodine intake may cause a subtle change in thyroid function even in subjects with normal thyroid function. We analyzed 337 subjects (64 men and 273 women; mean age, 49 years) who showed normal levels of thyroid peroxidase antibodies (TPO-Ab) and thyroglobulin antibodies (Tg-Ab) by measuring the urinary iodine excretion, free T4 (FT4), and thyroid-stimulating hormone (TSH). The results showed urinary iodine excretion had negative correlation with FT4 (γ = -0.11, p = 0.043) and showed a positive trend with TSH (γ = 0.10, p = 0.068). We found that 61.7% of subjects had circulating TPO-Ab within normal reference range. In all subjects, TPO-Ab levels were negatively correlated with FT4 (γ = -0.17, p = 0.002) and positively with TSH (γ = 0.13, p = 0.021). In conclusion, high iodine intake can negatively affect thyroid hormone levels in subjects with normal thyroid function. Population-based study will be helpful for further clarification.
authors.affiliation: Endocrinology, Severance Hospital Integrative Research Institute for Cerebral and Cardiovascular Diseases, Department of Internal Medicine, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, 120-752, South Korea.
authors.forename: Sena
authors.initials: S
authors.lastname: Hwang
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Lee
authors.forename: Dong Yeob
authors.initials: DY
authors.lastname: Shin
authors.forename: Eun Jig
authors.initials: EJ
authors.lastname: Lee
mesh_terms: D005260:Female; D006801:Humans; D007455:Iodine / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013960:Thyroid Function Tests
chemical_list: D007455:Iodine