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Thyroid dysfunction and autoantibodies 10 years after implementation of universal salt iodization: Tehran Thyroid Study
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P Heydarian   , F Azizi |
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Abstract: (25008 Views) |
| Introduction: Increased frequency of thyroid antibodies (Abs) following correction of iodine deficiency has been reported in several studies, although its clinical implications are still unclear. Ten years after initiation of universal salt iodization, the prevalence of thyroid dysfunction and antibodies were investigated in Tehran adults. Material and Methods: A systematic sample of 1434 people aged >20 years, selected from Tehran Lipid and Glucose Study population, participated in this cross-sectional study from Dec 1999 to Sept 2000. Thyroid size was graded according to WHO grading system and thyroid nodules were detected by palpation. A fasting blood sample was taken for serum TSH, total T4, T3 uptake, antithyroperoxidase (TPOAb), and antithyroglobulin (TgAb) antibodies. Urinary iodine concentration was measured for a random subsample of 160 people. In persons with no history of taking thyroid drugs during the previous month, overt and subclinical hypothyroidism was defined as TSH>3.5 μU/mL and low (<1.0) and normal FT4I, while overt and subclinical thyrotoxicosis as TSH<0.3 μU/mL and high (>4.2) and normal FT4I respectively. Results: Median urinary iodine concentration was 18.5 μg/dL. Total goiter prevalence decreased with age and was higher in women than men (33.0% vs.15.5%, P<0.001). In this study, 5.9% of people had thyroid nodules and the prevalence was higher in females than males (8.3% vs. 3.0%, P<0.001). The prevalence of overt and subclinical hypothyroidism were 3.5/1000 (1.6/1000 in males and 5.1/1000 in females) and 2.2% (0.9% in males and 3.2% in females), respectively. No new case of overt thyrotoxicosis was found and the prevalence of subclinical thyrotoxicosis was 4.2/1000 (3.1/1000 in males and 5.1/1000 in females). Mean TSH was higher in females than males (P<0.01). In women, positive Abs were more prevalent (P<0.001) and the frequency of TPOAb+ increased with age. The frequencies of TPOAb+ and TgAb+ were in agreement (P<0.001), 8.3% in men and 15.9% in women for TPOAb+ and 11.0% in men and 21.5% in women for TgAb+. In logistic regression model, TPOAb+, TgAb+ and female sex were determinants of TSH>3.5 μU/mL. On the other hand, TgAb+, TSH>3.5 μU/mL and goiter were determinants of TPOAb+. TPOAb+, TSH>3.5 μU/mL, nonsmoking and female sex were determinants of TgAb+. Using different categories for TSH in the model, TSH>0.3 μU/mL predicted TPOAb+ (Odds ratio=1.77, P<0.05) and TSH>2.1 μU/mL predicted TgAb+ (Odds ratio=1.73, P<0.05). Conclusion: There is a relatively high prevalence of subclinical hypothyroidism in Tehran adults. One decade after initiation of universal salt iodization, the association between positive Abs with elevated TSH and goiter suggests the pathogenic importance of thyroid Abs, especially TPOAb. |
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| Keywords: Thyroid autoantibody, Hypothyroidism, Hyperthyroidism, Goiter, Thyroid nodule, Urinary iodine |
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Full-Text [PDF 423 kb]
(10262 Downloads)
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Type of Study: Original |
Subject:
Endocrinology
Received: 2006/11/22 | Published: 2002/12/15
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