Isfahan Thyroid Cohort Study (ITCS).

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.

A Thyroid Stimulating Hormone Reference Range: Iranian Thyroid Cohort study.

BACKGROUND: Current reference values for thyroid function tests are derived from data from different ethnicities and geographical areas. In this article, we aim to select criteria from the guidelines proposed by the National Academy of Clinical Biochemistry (NACB) and to determine the TSH and T4 reference limits in the iodine-sufficient area of Isfahan, a metropolitan city in Iran. MATERIALS AND METHODS: This study was conducted within the framework of "Isfahan Thyroid Study (ITS)", an ongoing prospective cohort that started in 2006 (n=2523) until 2011 (n=711) and included participants above the age of twenty. We measured TSH, total T4, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb). RESULTS: Recruitment was based on the NACB criteria, 1899 participants were included in 2006(58.5% male) and 377 in 2011(62.3% male). The mean± SD age was 39.66 ±12.71 and 48.96±12.35 years in 2006 and 2011, respectively. The mean± SD for TSH was 2.0±1.19 and 2.11±1.11 mU/L and T4 was 6.67±1.47 and 8.3±2.95 µg /dl in 2006 and 2011, respectively. In 2006, the 2.5th percentile of serum TSH levels was 0.4 mU/L (males: 0.4 mU/L, females: 0.5 mU/L) and the 97.5th percentile of serum TSH was 4.96 mU/L (males: 4.72 mU/L, females: 5. 3 mU/L). In 2011, the 2.5th percentile of serum TSH levels was 0.7 mU/L (males: 0.6 mU/L, females: 0.77 mU/L) and 97.5th percentiles of serum TSH was 4.9 mU/L (males: 5.7 mU/L, females: 5. 57 mU/L). CONCLUSION: This study determined age and sex specific TSH and T4 reference ranges in the Isfahanian population, which could theoretically enable clinicians to classify patients more accurately. (www.actabiomedica.it).

Effect of Vitamin D deficiency treatment on thyroid function and autoimmunity markers in Hashimoto's thyroiditis: A double-blind randomized placebo-controlled clinical trial.

BACKGROUND: The link between autoimmune thyroid diseases and Vitamin D deficiency has been reported. However, there are controversies in this regard. We conducted a double-blind randomized placebo-controlled clinical trial to investigate the effect of Vitamin D deficiency treatment on thyroid function and autoimmunity marker (thyroid peroxidase antibody [TPO-Ab]) in patients with Hashimoto's thyroiditis. MATERIALS AND METHODS: Fifty-six patients with Hashimoto's thyroiditis and Vitamin D deficiency (25-hydroxyvitamin D level ≤20 ng/mL) were randomly allocated into two groups to receive Vitamin D (50000 IU/week, orally) or placebo for 12 weeks, as Vitamin D-treated (n = 30) and control (n = 26) groups, respectively. TPO-Ab, thyroid-stimulating hormone (TSH), parathormone, calcium, albumin, and creatinine concentrations were compared before and after trial between and within groups. The data were presented as mean (standard error [SE]) and analyzed by appropriate tests. RESULTS: Mean (SE) of Vitamin D was increased in Vitamin D-treated group (45.5 [1.8] ng/mL vs. 12.7 [0.7] ng/mL, P = 0.01). Mean (SE) of TPO-Ab did not significantly change in both groups (734 [102.93] IU/mL vs. 820.25 [98.92] IU/mL, P = 0.14 in Vitamin D-treated and 750.03 [108.7] [IU/mL] vs. 838.07 [99.4] [IU/mL] in placebo-treated group, P = 0.15). Mean (SE) of TSH was not changed in both groups after trial, P = 0.4 and P = 0.15 for Vitamin D-treated and control groups, respectively. No significant difference was observed between two study groups in none studied variables (P > 0.05). CONCLUSION: Vitamin D treatment in Vitamin D deficient patients with Hashimoto's thyroiditis could not have significant effect on thyroid function and autoimmunity.

Effects of Vitamin D deficiency treatment on metabolic markers in Hashimoto thyroiditis patients.

BACKGROUND: The aim of the current trial was to investigate the effect of Vitamin D treatment on metabolic markers in people with Vitamin D deficiency and thyroid autoimmunity. MATERIALS AND METHODS: In this double-blind, randomized, placebo-controlled clinical trial, 65 Vitamin D deficient euthyroid or hypothyroid patients with positive TPO-Ab were enrolled. They randomly allocated into two groups to receive oral Vitamin D3 (50000 IU weekly) and placebo for 12 weeks. Serum concentration of calcium, phosphorus, albumin, C-reactive protein, blood urea nitrogen, creatinine, glycated hemoglobin (HbA1c), insulin, fasting plasma glucose (FPG), triglyceride (TG), total cholesterol, and high-density lipoprotein were measured in both groups before and after the trial. Homeostasis model assessment estimates of beta cell function (HOMA-B) and HOMA-insulin resistance (HOMA-IR) were calculated before and after trial in both groups. RESULTS: Thirty-three and thirty-two participants were allocated to Vitamin D-treated and placebo-treated groups, respectively. Mean (standard error) level of Vitamin D increased significantly in Vitamin D-treated group (45.53 [1.84] ng/mL vs. 12.76 [0.74] ng/mL, P = 0.001). The mean of HbA1c and insulin was increased significantly both in Vitamin D-treated and placebo-treated groups (P < 0.05). Other variables did not meet a significant change after trial (P = NS). In between-group comparison, there was not any significant difference between Vitamin D-treated and placebo-treated groups regarding measures of HOMA-B, HOMA-IR, FPG, HbA1c, and TG (P = NS). CONCLUSION: Our findings showed that weekly 50000 IU oral Vitamin D3 for 12 weeks did not improve metabolic markers, IR, or insulin secretion in Vitamin D deficient patients with Hashimoto thyroiditis.

The TSH levels and risk of hypothyroidism: Results from a population based prospective cohort study in an Iranian adult's population.

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.

The prevalence of thyroid dysfunction in an iodine-sufficient area in Iran.

BACKGROUND: The prevalence of hypothyroidism in Iran is unknown. The aims of the present study were to estimate the prevalence of overt and subclinical hypothyroidism among the adult population of Isfahan, a large metropolitan city in Iran, 15 years after universal salt iodization. METHODS: A cross-sectional survey was conducted from January 2006 through April 2006. The selection was conducted by stratified probability cluster sampling through household family members in Isfahan, Iran. Thyroid stimulating hormone (TSH) of 2523 men and women aged >20 years (mean: 39.0) was measured. Additional thyroid tests were done and serum levels of antithyroid antibodies were evaluated in individuals with elevated TSH. Elevated TSH with normal free T4 index (FT4I) at the second measurement was considered as subclinical and high TSH with low FT4I as overt hypothyroidism. RESULTS: The overall prevalence of hypothyroidism was 4.8% [95% confidence interval (CI) 3.7, 6.1] in men and 12.8% (95% CI 10.9, 14.6) in women; and 37.6% of hypothyroid men and women had positive antithyroperoxidase antibodies and/or antithyroglobulin antibody, while 19.3% of men and women were euthyroid. The mean (SE) of urinary iodine was 20.3 (0.55) microg/dL and 20.1 (1.37) microg/dL for euthyroid and hypothyroid individuals, respectively (P=0.65). Older age, female sex, and goiter were strongly associated with both overt and subclinical hypothyroidism. CONCLUSION: Hypothyroidism appears to be common in Isfahan, Iran. The high prevalence of hypothyroidism in Isfahan may be due to autoimmunity with no correlation to iodine intake.