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Background: The Isfahan Thyroid Cohort Study (ITCS) is one of the few population-based epidemiological studies in Iran that investigates the prevalence and incidence of thyroid disorders including hypothyroidism, hyperthyroidism, goiter, nodule, and iodine status., Methods: This cohort is located in Isfahan, Iran. The first phase was initiated in 2006 with 2523 participants (1275 males, 1248 females). The participants were selected using multi-stage cluster sampling from the general residents of Isfahan, Iran. The study had two phases (2006 and 2011) and its third stage is planned for 2020-2021., Results: The prevalence of thyroid function states was euthyroid (89.3%, 95% CI: 88%-90%), overt hypothyroidism (2.8%, 95% CI: 2%‒3%), subclinical hypothyroidism (5.8%, 95% CI: 4%-6%), overt hyperthyroidism (0.8%, 95% CI: 0.4%‒1%), and subclinical hyperthyroidism (0.99%, 95% CI: 0.6%-1%). Hypothyroidism and hyperthyroidism were significantly associated with goiter. The incidence of thyroid dysfunction was reported as follows: overt hypothyroidism (2.7, 95% CI: 1.6-3.7), subclinical hypothyroidism (20.6, 95% CI: 18-23), overt hyperthyroidism (1.9, 95% CI: 1-2.7) and subclinical hyperthyroidism (2.7, 95% CI: 1.6-3.7) per 1000 (person-year)., Conclusion: We assessed the prevalence and incidence of thyroid disorders in Isfahan in the first and second phase, respectively. We are conducting the third phase of the ITCS in order to study the associations between thyroid peroxidase antibody (TPOAb) level and environmental factors such as infection., (© 2021 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.)

Background: The prevalence of thyroid dysfunction is high in Isfahan, an area of iodine sufficient in Iran. The aim of this study is to investigate the incidence of thyroid dysfunctions in adults of metropolitan Isfahan and to determine the role of thyroid autoantibodies., Methods: In a population-based cohort study in 2006-2011, we measured TSH, T4, T3, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) in 618 out of 2254 people who were euthyroid in 2006. The incidence rates per 1000 person-year (pr) were calculated. The odds ratio (OR), relative risk (RR), and 95% confidence interval (95% CI) were calculated based on logistic regression to quantify the potential predictors of thyroid dysfunction. The receiver-operator characteristic (ROC) analysis along with area under the curve (AUC) was used to determine the optimal cutoff values for baseline TPOAb and TgAb as predictors of thyroid dysfunction., Results: Within a 6-year follow-up, the incidence rate of hypothyroidism was 3.3 in women and 2.1 in men while the incidence rate of hyperthyroidism was 3.8 in women and none in men per 1000 (person-year). A cutoff value of TPOAb at 38 IU/mL was obtained to differentiate the patients with hypothyroidism and hyperthyroidism, with specificity of 0.75 and sensitivity of 0.76, and AUC (CI 95%) of 0.882 (0.743-1.02), P = 0.01 and 0.817 (0.600-1.035) P = 0.033, respectively. There is a statistically significant association of hypothyroidism and hyperthyroidism with positive TPOAb [RR (CI 95%): 1.99 (1.27-3.13) and 2.20 (1.23-3.95), respectively]., Conclusions: The incidence rate of thyroid dysfunction is high in Isfahan, and higher TPOAb concentration is its strong predictor.

Objective: The aim of current study was to assess the relationship between serum TSH levels and hypothyroidism risk in the euthyroid population., Methods: In a population-based cohort study, a total of 615 individuals with a normal baseline TSH, from of total population (n=2254) in 2006, were followed up for 6years. TSH, total T4, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured. The relative risk (RR) and 95% confidence interval (95%CI) were calculated based on logistic regression. The Receiver Operating Characteristic (ROC) analysis along with area under the curve (AUC) was used to prediction of future hypothyroidism., Results: TSH level in 2006 was a significant predictor for overt hypothyroidism, in the total population (RR=3.5) and female (RR=1.37) (all, P value<0.05). A cutoff value of TSH at 2.05mIU/L [AUC: (CI95 %), 0.68 (0.44-0.92; P=0.05)] was obtained for differentiating the patients with overt hypothyroidism from euthyroid. However, this cut off was not observed when we included only negative TPO and TgAbs people in 2006. The RR of hypothyroidism increased gradually when TSH level increased from 2.06-3.6mIU/L to >3.6mIU/L in the total population and both sexes. In women, the risk of overt hypothyroidism was significantly higher in subjects with TSH above 3.6 than those subject with THS levels≤2.05 [RR: (CI95 %), 20.57(2.-207.04), P value<0.05]., Conclusion: A cutoff value of TSH at 2.05mIU/L could predict the development of overt hypothyroidism in future. However, it was not applicable for people with negative TPOAb and negative TgAb., (Copyright © 2016 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.)

Background: The Isfahan Thyroid Cohort Study (ITCS) is one of the few population-based epidemiological studies in Iran that investigates the prevalence and incidence of thyroid disorders including hypothyroidism, hyperthyroidism, goiter, nodule, and iodine status. Methods: This cohort is located in Isfahan, Iran. The first phase was initiated in 2006 with 2523 participants (1275 males, 1248 females). The participants were selected using multi-stage cluster sampling from the general residents of Isfahan, Iran. The study had two phases (2006 and 2011) and its third stage is planned for 2020-2021. Results: The prevalence of thyroid function states was euthyroid (89.3%, 95% CI: 88%-90%), overt hypothyroidism (2.8%, 95% CI: 2%-3%), subclinical hypothyroidism (5.8%, 95% CI: 4%-6%), overt hyperthyroidism (0.8%, 95% CI: 0.4%-1%), and subclinical hyperthyroidism (0.99%, 95% CI: 0.6%-1%). Hypothyroidism and hyperthyroidism were significantly associated with goiter. The incidence of thyroid dysfunction was reported as follows: overt hypothyroidism (2.7, 95% CI: 1.6-3.7), subclinical hypothyroidism (20.6, 95% CI: 18-23), overt hyperthyroidism (1.9, 95% CI: 1-2.7) and subclinical hyperthyroidism (2.7, 95% CI: 1.6-3.7) per 1000 (person-year). Conclusion: We assessed the prevalence and incidence of thyroid disorders in Isfahan in the first and second phase, respectively. We are conducting the third phase of the ITCS in order to study the associations between thyroid peroxidase antibody (TPOAb) level and environmental factors such as infection. [ABSTRACT FROM AUTHOR]