No significant association between stable iodine intake and thyroid dysfunction in children after the Fukushima Nuclear Disaster: an observational study.

PURPOSE: Stable iodine prophylaxis helps prevent childhood thyroid cancer in nuclear emergencies; however, there is limited information on its effect on thyroid function. This study aimed to examine thyroid function and autoimmunity among children and adolescents that took stable iodine after the Fukushima Nuclear Disaster. METHODS: For this observational study, data were obtained from children and adolescents that underwent thyroid cancer screening at Hirata Central Hospital from April 2012 to March 2018. Participant characteristics, including possible hypothyroidism and hyperthyroidism, were compared between the prophylaxis and no-prophylaxis groups. Multivariable logistic regression models were used to assess for possible hypothyroidism, autoantibodies positive, and hyperthyroidism. RESULTS: A total of 1,225 participants with stable iodine prophylaxis and 3,946 without prophylaxis were enrolled. Of those participants, blood samples were available for 144 and 1,201 participants in the prophylaxis and no-prophylaxis groups, respectively. There were 17 (11.8%) and 146 cases (12.2%) of possible hypothyroidism or autoantibodies positive cases in the prophylaxis and no-prophylaxis groups, respectively, and there were no cases and 3 cases (0.2%) of possible hyperthyroidism in those two groups, respectively. Multivariable analysis for possible hypothyroidism revealed no association between stable iodine intake and possible hypothyroidism or autoantibodies positive [odds ratio 0.716 (95% confidence interval 0.399-1.284)] (p = 0.262). We did not perform multivariable analysis for hyperthyroidism due to the limited number of cases. CONCLUSION: Significant adverse effects of stable iodine intake on thyroid function were not observed among children and adolescents 7 years after the Fukushima Nuclear Disaster.

Risk perception regarding implementation of iodine thyroid blocking during a nuclear disaster of mothers living near a nuclear power station in Japan.

Pre-emptive evacuation orders following the accident at the Fukushima Daiichi Nuclear Power Station (FDNPS) in March 2011 and subsequent regulatory limits regarding contaminated food, milk, and water minimized the external and internal radiation exposure doses of nearby residents. However, with regard to implementation of iodine thyroid blocking (ITB), residents were confused because no information on the matter was released by the central and/or local governments. Based on lessons learned from the FDNPS accident, many countries have revised their guidelines regarding ITB during nuclear disasters. To adequately revise such guidelines and ensure effective ITB implementation during a nuclear disaster, however, residents' perceptions of ITB must be clarified. In this study, the perception of risks associated with ITB was investigated in mothers residing near the Sendai Nuclear Power Plant (SNPP) in Kagoshima Prefecture, Japan. Of the 520 mothers surveyed, 467 (89.8%) expressed anxiety regarding the administration of potassium iodine (KI) to their children. Logistic regression analysis revealed that the mothers' anxiety regarding the administration of KI to their children was positively correlated with their wish to consult an expert about KI and their hesitation to let their children eat foods produced in Fukushima, and negatively correlated with having confidence about administering KI to their children. Careful communication of potential risks to mothers residing near nuclear power plants is thus critical for implementing effective ITB in children.

Immunomodulatory effect of vitamin D and its potential role in the prevention and treatment of thyroid autoimmunity: a narrative review.

The main role of vitamin D is to control mineral homeostasis. However, recent studies suggested the existence of a number of extraskeletal effects. Among the latter, preclinical studies provided consistent data on the involvement of vitamin D in innate and adaptive immunity and autoimmunity. Molecular biology studies showed that both vitamin D receptor and vitamin D enzymatic complexes are expressed in a large number of cells and tissues unrelated to mineral homeostasis. In contrast, only a few randomized clinical trials in humans investigated the possible role of vitamin D in the prevention or treatment of immunological disorders. In this regard, low serum vitamin D levels have been reported in observational trials in human autoimmune disorders. The aim of the present paper was to review the potential implications of vitamin D in immune modulation, with special focus on thyroid autoimmune disorders.

The Impact of l-Thyroxine Treatment of Donors and Recipients on Postoperative Outcomes After Heart Transplantation.

OBJECTIVE: The effect of thyroid dysfunction on adverse outcomes has been studied in many different patient populations. The objective of this study was to investigate the effect of thyroid hormone supplementation of donors and recipients on postoperative outcomes after orthotopic heart transplantation. DESIGN: Retrospective. SETTING: Single center, university hospital. PARTICIPANTS: Two-hundred and sixty-six consecutive patients undergoing heart transplantation. INTERVENTIONS: No interventions. MEASUREMENTS AND MAIN RESULTS: Demographic, hemodynamic, and clinical characteristics; donor and recipient United Network for Organ Sharing scores; and information on thyroid hormone support of donors and recipients were recorded. During the median follow-up of 4.59 years (interquartile range 4.26-4.92 y), 70 patients (26.3%) died. After adjustments were made for the United Network for Organ Sharing score, recipients who were treated preoperatively with l-thyroxine had a lower risk for all-cause mortality (adjusted hazard ratio [HR] 0.24, 95% confidence interval [CI] 0.06-0.98; p = 0.047) compared with recipients who were not treated with l-thyroxine. In addition, l-thyroxine treatment of donors was associated with a better recipient survival (HR 0.31, 95% CI 0.11-0.87; p = 0.025). CONCLUSIONS: Pretransplantation thyroid hormone supplementation of donors and recipients was associated with improved long-term survival after heart transplantation.

The impact of mandatory iodine fortification and supplementation on pregnant and lactating women in Australia.

BACKGROUND AND OBJECTIVES: In Australia, two public health measures were introduced between 2009 and 2010 to reduce iodine deficiency. However there has been a shortage of information regarding their effectiveness and the ongoing prevalence of iodine deficiency in Australia. The primary aim of this study was to assess the extent to which these public health measures have reduced rates of iodine deficiency among pregnant and lactating women. METHODS AND STUDY DESIGN: A review was conducted to identify all studies published since January 2010 that quantitatively measured the iodine status of pregnant and/or lactating women in Australia. RESULTS: We found 25 publications, of which seven were included in this review after our exclusion criteria were applied. Of the seven included publications, three demonstrated the pregnant and lactating women in their studies to be iodine replete (median urinary iodine concentrations (MUIC) greater than 150 µg/L, or a breast milk iodine concentration (BMIC) of greater than 100 µg/L). The remaining four publications found MUIC of pregnant and lactating women to be below the 150 µg/L threshold, in the mild-to-moderate iodine deficiency category. Only two studies, documented iodine sufficiency among pregnant and lactating women in the absence of iodine supplementation. CONCLUSIONS: Many pregnant and lactating women in Australia remain at least mildly iodine deficient. Antenatal iodine supplementation was the factor most consistently associated with an adequate iodine status. Larger, more representative studies or sentinel studies with a National coordination are needed to understand the differences in iodine status that exist across the country.

Prevalence of thyroid diseases in the population of the town of Piekary Slaskie in the years 2006-2011 on the basis of the implemented prevention program.

Epidemiological investigations regarding the incidence of thyroid diseases reveal that in the Silesia thyroid diseases constitute 13.5% of all illnesses in Poland. AIM: The aim of this study was to analyze the structure of thyroid diseases in Piekary Slaskie in the years 2006-2011 and evaluate the effectiveness of the implemented Thyroid Disease Prevention Programme. MATERIALS AND METHODS: The material comprised the thyroid test results of 1137 patients who consented to take part in the Thyroid Disease Prevention Program in the years 2006-2011. The patients who underwent the examination constituted 2.04% of the whole population residing in Piekary Slaskie. Assessment of thyroid function was based on hormonal measurements (thyroid-stimulating hormone, TSH), thyroid ultrasound, ultrasound-guided fine needle aspiration biopsy of thyroid. RESULTS: The examinations conducted in 1137 participants of the Thyroid Disease Prevention Programme in the years 2006-2011 prove that the program allowed to diagnose thyroid nodular lesions in 44.1% of examined people, thyroiditis in 57.5% of patients, increased thyroid volume in 27.1% of subjects, hypothyroidism or hyperthyroidism in 26.9% of examined patients, and neoplastic disease in 1.1% of patients. CONCLUSIONS: The Thyroid Disease Prevention Program being the subject of assessment has met its objective aimed at prophylaxis in Piekary Slaskie, as thanks to the conducted diagnostic procedures, it allowed to provide treatment of thyroid diseases at their different stadiums.

Secondary and tertiary preventions of thyroid disease.

INTRODUCTION: Secondary and tertiary preventions are concerned with the recognition of the disease process in a very early stage and delay in progression to complete disease and minimization of complications and the impact of illness. METHODS: All articles related to secondary and tertiary prevention of thyroid diseases were reviewed. Using related key words, articles published between 2001 and 2015 were evaluated, categorized, and analyzed. RESULTS: In secondary prevention, congenital hypothyroidism and subclinical hypo and hyperthyroidism are equally important. Routine screening of patients with multinodular goiter by either ultrasonography or calcitonin is a controversial issue, while calcitonin assessments in medullary cancer and RET in family members are recommended. Screening of thyroid disease in pregnancy is limited to those with risk factors. Views regarding the importance of thyroid autoimmunity in secondary prevention are also presented. In tertiary prevention, prescribing excessive doses of levothyroxine, in the elderly in particular and appropriate care of all patients to avoid progression and complications are the key issues. CONCLUSION: Optimization of management of thyroid diseases requires timely screening, prevention of progression to more sever disease, optimal medical care, and avoidance of iatrogenic conditions.

Sunshine vitamin and thyroid.

Vitamin D exerts its canonical roles on the musculoskeletal system and in the calcium/phosphorus homeostasis. In the last years, increasing evidences suggested several extra-skeletal actions of this hormone, indicating that vitamin D may produce effects in almost all the body tissues. These are mediated by the presence of vitamin D receptor (VDR) and thanks to the presence of the 1-α-hydroxylase, the protein that converts the 25-hydroxyvitamin (calcidiol) to the active form 1,25-dihydroxyvitamin (calcitriol). Several studies evaluated the possible role of vitamin D in the pathogenesis of thyroid diseases, and this review will focus on the available data of the literature evaluating the association between vitamin D and thyroid function, vitamin D and autoimmune thyroid diseases, including Hashimoto's thyroiditis, Graves' disease and post-partum thyroiditis, and vitamin D and thyroid cancer.

Monitoring the effects of iodine prophylaxis in the adult population of southern Italy with deficient and sufficient iodine intake levels: a cross-sectional, epidemiological study.

I prophylaxis is the most effective strategy to eradicate I deficiency disorders, but it has been shown to affect the thyroid disease pattern. In this study, we assessed the frequency of thyroid disorders in an adult population living in two areas of southern Italy after implementing I prophylaxis. To this aim, a cross-sectional, population-based study including 489 subjects from an I-deficient rural and an I-sufficient urban area of southern Italy was conducted. Thyroid ultrasound was performed on all participants, and urine and blood samples were collected from each subject. The levels of thyroid-stimulating hormone (TSH), thyroglobulin (TgAb) and thyroperoxidase antibodies (TPOAb), urinary I excretion (UIE), and thyroid volume and echogenicity were evaluated. We found that the median UIE was higher in the urban than in the rural area (P=0·004), whereas the prevalence of subjects affected by goitre was higher in the rural compared with the urban area (P=0·003). Positive TgAb rather than TPOAb were more frequent in subjects from the urban area compared with the rural area (P=0·009). The hypoechoic pattern at thyroid ultrasound (HT-US) was similar between the two areas, but TgAb were significantly higher (P=0·01) in HT-US subjects from the urban area. The frequency of elevated TSH did not differ between the two screened populations, and no changes were found for TgAb positivity in subjects with high TSH in the urban compared with the rural area. Our findings support that the small risks of I supplementation are far outweighed by the substantial benefits of correcting I deficiency, although continued monitoring of populations is necessary.

Iodine nutritional status and thyroid effects of exposure to ethylenebisdithiocarbamates.

INTRODUCTION: Italy is still characterized by a mild iodine deficiency and is among the most intensive users of chemical products for agriculture in Europe. The aim of this study was i) to evaluate thyroid effects of exposure to mancozeb, a fungicide widely used in agriculture, in a sample of Italian grapevine workers, and ii) to verify whether the iodine intake may modulate the risk of thyroid disruption due to the mancozeb metabolite ethylenthiourea (ETU). METHODS: One hundred seventy-seven occupationally exposed male workers (29 from Chianti, a mild iodine deficient area, and 148 from Bolzano an iodine sufficient province) and 74 non-occupationally exposed male controls (34 from Chianti and 40 from Bolzano) were enrolled in the study. Serum biomarkers of thyroid function, as well as urinary iodine and ETU concentrations were assessed. Moreover all the recruited subjects underwent clinical examination and thyroid ultrasound. RESULTS: Multivariate comparisons showed lower mean serum levels of FT4 in Chianti-workers as compared to Bolzano-workers. Moreover, an increased urinary iodine excretion (>250µg/L) was more frequently found among more exposed workers (ETU>20µg/L) than among less exposed ones and this effect was more pronounced in Chianti- than in Bolzano-workers. Chianti-workers also showed a significantly higher frequency of very low thyroid volume (≤6.0ml) as compared to controls. CONCLUSIONS: These findings showed a mild thyroid disrupting effect due to occupational exposure to mancozeb, more pronounced in workers residing in an area characterized by a mild to moderate iodine deficiency as compared to workers residing in an area covered by a long-lasting iodine prophylaxis program.

[Treatment of CKD-MBD targeting the parathyroid gland].

Secondary hyperparathyroidism is a major component of chronic kidney disease-mineral and bone disorder (CKD-MBD) and has a considerable impact on morbidity and mortality through the development of high-turnover bone disease and vascular calcification. Thus, management of secondary hyperparathyroidism is important for improving the outcomes of CKD patients. Because there is a fundamental difference in the pathogenesis of secondary hyperparathyroidism between predialysis and dialysis patients, different therapeutic approach should be considered for each condition. In this article, we summarize the treatment of CKD-MBD for managing secondary hyperparathyroidism, with a particular focus on the difference between predialysis and dialysis stages of CKD.

[Solution of Iodine deficiency in the Czech Republic - history and current situation20 years of work of prof. Václav Zamrazil for Commission for the solution of Iodine deficiency]. / Resení jodového deficitu v Ceské republice - historie a soucasný stav20 let práce prof. MUDr. Václava Zamrazila v Meziresortní komisi pro resení jodového deficitu.

Diseases caused by Iodine deficit are preventable. Inter resort Commission for the solution of Iodine deficiency (MKJD) at State Institute for Health (SZU) in Prague has been taking effective measures which satisfied requirements of the Principles for sustainable elimination of diseases caused by Iodine deficiency ICCD WHO: 96 % of households is using iodized salt, average Iodine content is 25 mg/1 kg of salt. Data from studies show ioduria less 100 mcg/l in only 9 per cent of seniors, 5 % of children 7-10 years, 3 % of children 10-12 years. Under 50 mcg only 1 % of children 10-12 years. Median of iodurias is below 300 mcg/l (seniors 185 mcg/l, children 7-10 years 277 mcg/l, children 10-12 years 252 mcg/l). We satisfy 8 of 10 indicators of Principles for Sustainable elimination of diseases caused by Iodine deficiency. Results of screening for congenital hypothyroidism are in keeping with sufficient iodine intake in newborns. Unsatisfactory situation however persist in expectant and breast feeding mothers 16 % [11] 6 % [10] of women included in the respective studies had ioduria below 50 mpg/l. Milk and dairy produce became a rich dietary source of Iodine as cattle feeds are fortified with Iodine. No part of observed human population is exposed Iodine doses higher than 17 mcg/kg. Next target for prevention will be achieving optimal iodine concentration in milk and improvement of iodine saturation of expectant and nursing mothers. Integral part is the monitoring of iodine saturation of population.Key words: dietary exposition - dietary sources of iodine - Inter resort commission for elimination of iodine deficit - iodine deficiency - iodine supply - iodized salt - ioduria.

[Influence of radiating and chemical loads on changes of biochemical indices of the endocrine homeostasis in inhabitants from ecologically various areas of the Bryansk region].

There ecologic-hygienic ranging of all 27 areas of the Bryansk region was performed with the using of the innovative methodical approach with taking into account the integrated indices of total pollution of all objects of the environment. The analysis of results of the performed biochemical researches with studying of indices of the endocrine homeostasis in residents of ecologically various areas has allowed to evolve thyrotropic hormone TTH (Qcalc=2,4 at K=1,96) and thyroid hormone ST4 (Qcalc=3,684 at K=1,96) as biological markers of the negative impact of technogenic-chemical contamination of environment on human health.

[Assessment of the efficiency of prevention of iodine deficiency among the children's population of the city of Mezhdurechensk of the Kemerovo region].

In the article there are presented results of a study of indices of ioduria in preschool kids and school children of the city of Mezhdurechensk (south of the Kemerovo region). 411 children aged of 3-17 years participated in the study. The median of ioduria on preschooler kids was 97,0 pg/l, and the proportion of urine samples with iodine levels less than 50 pg/l - 1,0%. The median of ioduria in school children is 98,0 pg/l, the percentage of urine samples with iodine levels less than 50 pg/l accounts for 1,3%. On average, on the population of children there was established that the percentage of urine samples with iodine levels from 50-100 pg/l (mild deficiency) was detected in 53,5% of children. Comparative analysis of indices of the level of ioduria according to data obtained in 2008 and 2014 in a group of school children showed that the measures taken to prevent diseases caused by iodine deficiency (the use of iodized salt in the diet of children and adolescents from organized groups on a regular basis) have given positive results.

[Thyroid gland pathology in children population exposed to the combination of iodine deficiency and fluoride pollution of environment].

The article presents results of study of the impact of iodine deficiency and technogenic fluoride on the state of the thyroid gland in children. On the example of two districts of the city of Bratsk there were executed dynamic investigations (2002 and 2012), including the estimation of the pollution of ambient air and soil by fluorine compounds, levels of iodine intake by the body, the clinical examination of children aged from 5 to 7 years d and interviewing of their parents. In the course of the medical examination there were executed: physical examination by the pediatrician, endocrinologist, ultrasound examination of the thyroid gland, the determination both of serum hormone content by radioimmunoassay and urinary excretion offluorine and iodine. Concentrations of hydrogen fluoride and a solidfluorides in ambient air led to the accumulation offluoride ion in the soil. The iodine entering with drinking water and food, was established to provide only 37.5-50% of the daily requirement of iodine. Increased fluoride ion content in urine and milk teeth in children is associated with the concentrations of the fluorine-containing pollutants in the ambient air and soil. The fluoride pollution against the background of the natural iodine deficiency was established to increase the frequency of functional and morphological disorders of the thyroid gland in children.

The effect of Greek herbal tea consumption on thyroid cancer: a case-control study.

BACKGROUND: Although in the last decade several studies have addressed the protective role of black and green tea on several diseases, including cancer, there are only few and controversial studies on the effect of tea on benign and malignant thyroid diseases. METHODS: An age and gender group matched case-control study conducted in Athens, Greece, was designed. 113 Greek patients with histologically confirmed thyroid cancer and 286 patients with benign thyroid diseases along with 138 healthy controls were interviewed with a pre-structured questionnaire in person by trained interviewers. RESULTS: An inverse association between chamomile tea consumption and benign/malignant thyroid diseases was found (P < 0.001). The odds of chamomile tea consumption, two to six times a week, after controlling for age, gender and BMI, were 0.30 (95% CI: 0.10-0.89) and 0.26 (95% CI: 0.12-0.5) for developing thyroid cancer and benign thyroid diseases, respectively when compared with not consumption. The duration of consumption was also inversely associated with the diseases. Thirty years of consumption significantly reduced the risk of thyroid cancer and benign thyroid diseases development by almost 80%. Similar, although weaker protective association, was found for sage and mountain tea. Adjustment for smoking, alcohol and coffee consumption did not alter the results. CONCLUSIONS: Our findings suggest for the first time that drinking herbal teas, especially chamomile, protects from thyroid cancer as well as other benign thyroid diseases.

Radiocontrast-induced thyroid dysfunction: is it common and what should we do about it?

There has been a substantial increase in the use of radiocontrast-enhanced imaging studies in the past two decades (particularly computed tomography and coronary angiography). Sudden exposure to high levels of iodide may result in thyroid dysfunction (hyperthyroidism and hypothyroidism alike). Although the adverse-event rate is not very high, the condition is notable considering the large number of contrast-enhanced radiographic studies performed. Clinicians often have to decide on the most suitable diagnostic modality and the safest contrast medium when it comes to certain patients. In this study, we stress that the thyroid function of the patients should also be taken into consideration while making such decisions. We discuss in detail the prevalence and types (hypothyroidism and hyperthyroidism) of radiocontrast-induced thyroid dysfunction. We list the subsets of the population that are at a higher risk of radiocontrast-induced thyroid dysfunction and summarize the necessary prophylaxis and possible treatment. The presented principles apply to intravenous, intra-arterial and enteral (endoscopic retrograde cholangiopancreatography) routes of iodinated contrast medium administration.

Iodine nutritional status after the implementation of the new iodized salt concentration standard in Zhejiang Province, China.

BACKGROUND: Iodine deficiencies were prevalent in China until the introduction of universal salt iodization (USI) in 1995. In 2012, the standard salt iodine concentration was adjusted to 20-30 mg/kg. The success of USI for the control of iodine deficiency disorders requires monitoring its effect at a population level. METHODS: Two cross sectional surveys of a representative sample of children aged 8-10 years in Zhejiang Province were carried out in 2011 and 2013. Data on participants' socio-demographic characteristics were collected from the children using a structured questionnaire. Spot urine samples were collected and delivered to local Center for Disease Control and Prevention laboratory for measuring urinary iodine concentration. In 2011, out of 420 selected children aged 8-10 years, 391 were recorded and provided urine samples. In 2013, out of 1560 selected children aged 8-10 years, 1556 were recorded and provided urine samples. RESULTS: The median urinary iodine concentration of subjects in the 2013 survey was 174.3 µg/L, significantly lower than that of 2011(p = 0.000). The median urinary iodine concentration of subjects living in urban and rural areas in the 2013 survey was 169.0 µg/L, and 186.1 µg/L respectively, significantly lower than that of 2011 only for subjects living in urban areas (p = 0.000). There were no significant differences for subjects living in rural areas in the survey in 2011 and in 2013 (p = 0.086). CONCLUSIONS: At the time the new local iodization policy put forward, iodine nutrition was generally adequate in both urban and rural areas, suggesting that the new policy for adjusting the standard salt iodine concentration is effective. Our data also indicate that the reason people living in urban areas had a lower urinary iodine concentration than people in rural areas may be due to their preference for using non-iodized salt in the last 2 or 3 years. Maintaining USI at an appropriate level is an important part of preventing iodine deficiency disorders and should always be based on regular monitoring and comparison of urinary iodine concentration by province.

Beneficial effects of adequate iodine supply on characteristics of thyroid autonomy.

OBJECTIVE: Our aim was to establish the characteristics of thyroid autonomy (TA) in Slovenian patients and the required therapeutic dose of radioiodine before and ten years after the increase in mandatory salt iodization from previous 10 mg of potassium iodide to 25 mg per kg in 1999 because almost no data about TA and radioiodine treatment with respect to iodine supply are available. DESIGN: Retrospective clinical study. PATIENTS: We reviewed records of all patients referred for the first time in 1998 and 2009 to the Thyroid Department at the University Medical Centre Ljubljana which is a tertiary referral centre with a stable catchment area for more than 20 years. METHODS: TA was diagnosed by thyroid function, ultrasound, scintigraphy and negative TSH receptor antibodies. Demographic characteristics and the applied dose of radioiodine were evaluated. RESULTS: In 1998, significantly more patients presented with TA than in 2009 (383 of 3243, 11·8% and 333 of 4546, 7·3%, respectively, P < 0·001). In 1998, the ratio between hyperthyroid and euthyroid patients was higher than in 2009 (6:1 and 2·1:1, respectively, P < 0·001). In 1998, patients were younger than in 2009 (mean 63·8 ± 13·9 and 66·8 ± 14·9 years, respectively, P < 0·004). Hyperthyroid patients were older than euthyroid in both years (P < 0·001). In 1998, mean applied dose of radioiodine was significantly lower than in 2009 (713 ± 306 and 791 ± 194 MBq, respectively, P = 0·003). CONCLUSIONS: In adequate iodine supply, TA is less frequent, patients are less often hyperthyroid, they are older and cured with higher doses of radioiodine than in mild iodine deficiency.

Thyroid function in pregnant women: iodine deficiency after iodine enrichment program.

OBJECTIVE: Significant changes in thyroid function occur during pregnancy which can complicate the interpretation of thyroid function tests. Therefore, normative gestational related reference ranges for thyroid hormones tests are required. The aim of this study was to determine the reference ranges for free triiodothyronine (FT3), free thyroxin (FT4) and thyroid stimulating hormone (TSH) in Iranian pregnant women. METHODS: This study was a cross-sectional observational study conducted in the Obstetrics and Gynecology department, Akbarabadi University Hospital. A single blood sample from 584 pregnant women was analyzed for thyroid function. Serum levels of TSH, FT4, FT3, total T4 (TT4), T3 resin uptake (T3RU) and anti-thyroid peroxidase antibody (TPO Ab) were measured. Urinary iodine was determined in some cases. Reference intervals based on 2.5th and 97.5th percentiles were calculated. RESULTS: The composition of reference population comprising 584 women included 162 in first trimester and 422 in the third trimester. The 2.5th and 97.5th percentiles values were used to determine the reference ranges for FT3, FT4, TT4, T3RU and TSH. These values were T3 1.4 and 2.9 pmol/L, FT4 7.1 and 18 pmol/L, TT4 7.2 and 13.5 µg/dL and TSH 0.5 and 3.9 µg/L, respectively. The level of urinary iodine in 80.5% of the subjects was less than normal. CONCLUSIONS: Serum levels of thyroid hormones are different in Iranian population that could be due to racial differences or differences in iodine intake.