Iodine supplementation for pregnant women: a cross-sectional national interventional study.

BACKGROUND: Although Iran has been considered iodine replete since 2000, the first national survey of iodine intake among Iranian pregnant women in 2014 indicated that despite the adequate intake of iodine by the general population, this vulnerable group has moderate iodine deficiency. Therefore, in this national cross-sectional interventional study, we aimed to assess the iodine intake and thyroid function of Iranian pregnant women 2 years after implementing national iodine supplementation for this vulnerable group. MATERIALS AND METHODS: In this cross-sectional study, we conducted a national interventional survey of pregnant women. A total of 1200 pregnant women (400 women from each trimester) from 12 provinces of Iran were recruited from the antenatal care clinics from October 2018 to March 2019. The median urinary iodine concentration (MUIC), as an indicator of iodine status in three spot urine samples, was measured, along with the serum total T4 (TT4), thyrotropin (TSH), thyroglobulin (Tg), thyroid peroxidase antibody (TPO-Ab), and iodine content of household salt. RESULTS: The mean age of the cohort was 28 ± 6.2 years, with the mean gestational age of 22.7 ± 13.0 weeks. The overall MUIC (IQR) of pregnant women was 188 µg/L (124.2-263 µg/L). Also, the MUICs in the three trimesters of pregnancy were 174 µg/L (110-254), 175 µg/L (116-251), and 165 µg/L (114-235), respectively. The MUICs ≥ 150, 100-149, and < 100 µg/L were found in 63, 19.8, and 16.2% of the subjects, respectively. The mean TT4 level was 12 ± 4.5 µg/dL, and the median (IQR) level of TSH was 2.37 mIU/L (1.66-3.18 mIU/L). According to our local reference range, 118 (10.5%) pregnant women had subclinical hypothyroidism, 6 (0.53%) women had isolated hypothyroxinemia, and 65 (5.7%) women were TPO-Ab positive. Also, the median (IQR) level of Tg was 10.08 µg/dL (5.7-20.4 µg/dL), and the median iodine content of household salt was 29.6 µg/g; the iodine content was ≥ 30 µg/g in 85% of household salt. The results showed that more than 95% of households were under iodized salt coverage. CONCLUSION: The results of this study indicated that iodine supplementation with at least 150 µg of iodine per day improved the iodine intake of pregnant women. Except for subclinical hypothyroidism, the prevalence of clinical hypothyroidism, clinical/subclinical thyrotoxicosis, TPO-Ab positivity, and isolated hypothyroxinemia decreased significantly, which emphasizes the importance of iodine supplementation during pregnancy.

Continuously sustained elimination of iodine deficiency: a quarter of a century success in the Islamic Republic of Iran.

BACKGROUND: Iodine deficiency and related disorders were very common in Iran prior to 1996, when universal salt iodization (USI) was implemented and in 2000 Iran was declared iodine deficiency disorders (IDD) free. The aim of this study was to evaluate the adequacy of iodine intake by Iranian households in all 30 provinces of Iran, a quarter of a century after the intervention. METHODS: A total of 18,000 school-aged children (8-10 years with mean 8.7 ± 1 year) were included in this study. Urine samples were collected from all children for measurement of urinary iodine excretion and 1800, 210 and 3000 salt samples were randomly collected from the family kitchen, production site of 73 salt factories and distribution circles of 30 provinces, respectively. RESULTS: The median urinary iodine concentration (UIC) of participants was 161 µg/L. The proportion of children with UIC of, 20-49, 50-99 and ≥ 100 µg/L were 10.3, 15.9 and 73.7%, respectively. The mean (± SD) and median salt iodine values were 28.2 (± 12.6) and 31.7 ppm, at the production site, and 31.5 (± 13.6) and 29.6 ppm at the distribution circles, respectively. About 80% of factory salts had more than 20 ppm iodine. 98% of households consumed iodized salt, 80% had appropriate salt storage, and 83% of the household salts contained ≥ 20 ppm. CONCLUSIONS: Based on the results of this study, Iranian populations are consuming adequate iodine. The well-maintained and monitored USI program has improved the dietary iodine intakes of the population, and the country has achieved all criteria of a well-controlled IDD program.

Thyroid dysfunction in patients with impaired glucose metabolism: 11 year follow up from the Tehran Thyroid Study.

OBJECTIVES: This study aimed to assess the prevalence and incidence and predictive factors of thyroid disorders (TD) in patients with impaired glucose metabolism. METHODS: Prevalence of TD was calculated in patients with impaired glucose metabolism compared to healthy controls, aged over 30 years in phase 1 of the Tehran Thyroid Study (TTS). Follow up assessments were conducted every 3 yrs, after which incidence of TD was calculated and its correlations with age, sex, smoking, blood pressure, body mass index (BMI), thyroid peroxidase antibody (TPOAb), thyrotropin (TSH), insulin resistance index, triglycerides and cholesterol were assessed. RESULTS: Incidence of TD among 435 diabetics, 286 prediabetics, and 989 healthy controls at baseline was 14, 18, and 21 per 1000 patients per year, respectively, being significantly lower in diabetics than that in healthy controls, a difference however that was not significant after adjusting for the variables mentioned (OR:0.64, 95% CI: 0.39-1.01). The incidence of TD in subjects with baseline serum TSH>1.94 mU/L or TPOAb≥40 IU/ml in all three groups was higher than that in patients with TSH≤1.94 mU/L or TPOAb<40 IU/ml, and remained significant after variable adjustment. Baseline TSH>1.94 mU/L was predictive of TD with 70% sensitivity and specificity. Baseline serum TSH (ROC area: 0.73, 95% CI: 0.68-0.77) had better predictive value than TPOAb (ROC area: 0.65, 95% CI: 0.61-0.69) for developing TD. CONCLUSION: Incidence of TD in type 2 diabetics or prediabetics is not higher than healthy controls. It is however necessary to conduct thyroid tests in patients with TPOAb≥40 IU/ml or TSH>1.94 mU/L.

Inadequate iodine nutrition of pregnant women in an area of iodine sufficiency.

PURPOSE: I. R. Iran has been considered iodine replete since 2000, but iodine nutrition of vulnerable subjects is not clear. The main goal of this study was assessment of iodine nutrition and thyroid function in pregnant Iranian women. METHODS: A total of 1072 pregnant women from ten provinces in the different parts of the country were recruited from November to March 2014. Median urinary iodine concentration (UIC) as the measure of iodine status and serum free T4 (FT4), thyrotropin (TSH), thyroglobulin (Tg), anti-thyroglobulin and anti-thyroid peroxidase antibodies (TgAb and TPOAb) were measured. RESULTS: Mean ± SD age of the cohort was 27.0 ± 7.2 years and gestational age was 20.7 ± 10.0 weeks. The median UIC for pregnant women was 87.3 µg/L, being 92.1, 86.0 and 76.8 µg/L, in three trimesters of pregnancy, respectively. Median UIC of <100, 100-149, 150-249, 250-499 and ≥500 µg/L was found in 58.4, 19.8, 16.2, 5.13 and 0.46 % of subjects, respectively. Median (IQR) values in the first, second, and third trimesters were 1.7 (0.9-2.8), 2.1 (1.5-2.9), and 2.1 (1.4-2.8) mIU/L for TSH, and 16.4 (12.21-21.13), 14.34 (12.16-19.69), and 14/07 (12.02-18.64) pmol/L for FT4, respectively. The frequency of elevated serum TSH was 9.0 % (6.6 % subclinical, 2.4 % overt hypothyroidism). The frequency of low serum TSH was 0.6 %. The frequency of positive TPOAb was 7.6 %. CONCLUSIONS: Results of this study have clarified that despite iodine sufficiency of school children in Iran, pregnant women have moderate iodine deficiency and need iodine supplementation.

Reference limit of thyrotropin (TSH) and free thyroxine (FT4) in thyroperoxidase positive and negative subjects: a population based study.

BACKGROUND: Current reference values for thyroid function tests are based on data from different ethnicities and geographical areas. The aim of the present study was to determine reference intervals for thyrotropin (TSH) and free T4 (FT4), based on the criteria of the National Academy of Clinical Biochemistry (NACB) in an Iranian population. MATERIAL AND METHODS: This study was conducted within the framework of Tehran Thyroid Study (TTS), an ongoing prospective cohort of 5704 randomly selected individuals, age ≥ 20 yr. A total of 2199 individuals (43.3% male, 56.7% female), based on NACB criteria were included in this study. Reference limit analysis was performed for the negative thyroid peroxidase antibody (TPOAb) group. RESULTS: After applying all exclusion criteria except TPOAb positivity (10.5%), data of 2459 participants remained for analysis. Of these, 953 (43.3%) were males and 1246 (56.7%) were females; the mean ± SD age was 43.53 ± 14.16 yr. The mean ± SD and median+IQR for TSH were 1.77 mU/l ± 1.24 and 1.46 (0.93-2.23) mU/l, respectively. The 2.5th and 97.5th percentiles TSH were 0.32 mU/l and 5.06 mU/l respectively. The mean ± SD and median (IQR) for FT4 for all negative TPOAb subjects were 1.19 ± 0.16 and 1.18 (1.08-1.31) ng/dl respectively. CONCLUSION: Reference ranges for thyroid function tests need to be derived from national databases. This study determined age and sex specific TSH and FT4 reference ranges in a Tehranian population, which could eventually enable clinicians to classify patients more appropriately.

Management of thyroid peroxidase antibody euthyroid women in pregnancy: comparison of the american thyroid association and the endocrine society guidelines.

The presence of thyroid autoantibodies is relatively high in women of childbearing age. There is evidence that positive thyroperoxidase antibody even in euthyroid women may increase the risk of spontaneous and recurrent pregnancy loss and preterm delivery. However, the evidence is not enough to justify recommendation on the screening of pregnant women for thyroid autoantibodies or LT4 supplementation for reducing maternal or fetal complications. In this paper we reviewed the related evidence and compared the new guidelines of the American Thyroid Association and Endocrine Society with respect to the screening and management of positive thyroperoxidase antibody in euthyroid pregnant women. As there was no major contradiction or disagreement between the two guidelines, either one of two guidelines may be used by clinicians for the appropriate management of thyroid autoimmunity during pregnancy.

The association of cigarette smoking with serum TSH concentration and thyroperoxidase antibody.

BACKGROUND: Although several studies have found an association between tobacco smoking and thyroid disorders such as Graves' disease, Graves' ophtalmopathy, goiter and thyroid multi nodularity, the effect of smoking on thyroid function is controversial. AIM: The aim of this study was to evaluate the association between smoking and serum TSH concentration and the presence of thyroperoxidase antibody (TPO Ab) in Tehranian adults. SUBJECTS AND METHODS: In this cross sectional community based survey, 1,581 randomly selected subjects with no history of thyroid disorders were studied within the framework of Tehran Lipid and Glucose Study. Serum TSH and TPOAb were measured in a fasting serum sample. Weight and height were measured and BMI was calculated. Smokers were classified into ever and never smokers based on the declaration of participants. RESULTS: Mean Ln TSH values in the ever smoker (0.36±0.82) was significantly lower than the never smoker (0.6±0.82) group (p<0.001) even after adjustment for age and BMI. The odds ratio for hypothyroidism (TSH>5.8) was 0.4 in the ever smoker group compared to the never one (odds ratio 0.4, 95% CI=0.2-0.8). The frequency of positive TPOAb in never smokers was significantly higher than ever smokers (%13.5 vs. % 6.7, p<0.001). CONCLUSION: The results suggest that smoking is associated with decreased serum TSH concentrations, lower risk of hypothyroidism and possibly with a lower frequency of thyroid auto immunity.

The incidence of thyroid function abnormalities and natural course of subclinical thyroid disorders, Tehran, I.R. Iran.

BACKGROUND: Despite the high prevalence of thyroid dysfunction, the epidemiology and natural course of these disorders have not been identified yet. AIM: The present survey was conducted to determine the incidence of thyroid dysfunction and natural course of subclinical thyroid disorders in an urban community of Tehran, I.R. Iran. SUBJECTS AND METHODS: Serum TSH and thyroperoxidase antibody (TPOAb) were measured at baseline and after 6.7 yr from a sample of 1999 randomly selected subjects aged≥20 yr, participants of the Tehran Lipid and Glucose Study (TLGS). Median TSH value and 2.5, 5, 95, and 97.5 TSH percentiles were determined at baseline using data obtained from 808 negative TPOAb subjects with no history of any thyroid disease or surgery, goiter, nodule, taking thyroid hormone preparations or anti-thyroid drugs. In those with abnormal TSH level, total T4 and T3 uptake were measured and free T4 index was calculated. RESULTS: Normal TSH reference range was 0.4-5.8 µU/ml according to the 2.5 and 97.5 TSH percentiles. The incidence rates of thyroid function abnormalities in 1000 subjects per year were as follows: clinical hypothyroidism: 0.28 in women and 0.21 in men; subclinical hypothyroidism: 11.59 in women and 4.69 in men; clinical hyperthyroidism: 1.4 in women and 0.21 in men; and subclinical hyperthyroidism: 5.72 in women and 3.62 in men. A significant increase was found in the frequency of positive TPOAb in women from 15.9 to 17.7% (p=0.006). Of 8 women with subclinical hypothyroidism at baseline, 5 remained unchanged, 1 became normal, and 1 developed clinical hypothyroidism at followup. Two women with subclinical hyperthyroidism normalized at follow-up. Of 2 men with subclinical hypothyroidism at baseline, 1 remained unchanged, whereas the other progressed to clinical hypothyroidism. CONCLUSION: After a 6.7 yr follow-up significant increase in the incidence of subclinical thyroid disorders was observed in both men and women, as compared to overt thyroid dysfunction. Increase in the prevalence of TPOAb positivity was observed only in women.

Differences between subjects with sufficient and deficient urinary iodine in an area of iodine sufficiency.

BACKGROUND: Iran has long been recognized as a country of iodine sufficiency; however, recent studies show that the proportion of subjects with insufficient urinary iodine is gradually increasing in Tehran capital city. AIM: The aim of this study was to evaluate differences between individuals with sufficient and deficient urinary iodine in Tehran. MATERIAL AND METHODS: In this cross-sectional study, 639 Tehranian adult subjects, aged ≥ 19 yr (242 males, 397 females), were enrolled through randomized cluster sampling. A 24-h urine sample was collected for measurement of urinary iodine, sodium and creatinine concentrations using the digestion method, flame photometry and autoanalyzer assay, respectively. Salt intake was estimated and iodine content of household salt was measured by titration. RESULTS: Medians (interquartile range) of 24-h urinary iodine concentrations in subjects with sufficient and deficient urinary iodine were 163.0 (126.0-235.0) and 44.0 (26.0-67.0) µg/l, p<0.001, respectively. Salt with iodine content of >20 parts per million was consumed by 77.4 and 38.3% of subjects with sufficient and deficient urinary iodine, respectively (p<0.001). Median daily salt intake in subjects with sufficient urinary iodine was significantly higher than in those with deficient urinary iodine (8.1 vs 7.3 g, p<0.001). No significant differences in the mentioned variables were observed between males and females. Fifty and 30% of subjects with insufficient and sufficient urinary iodine had <7 yr education, respectively (p<0.001). CONCLUSIONS: Iodine content of salt, the amount of salt intake and education levels differ greatly between subjects with sufficient and deficient urinary iodine in Tehran.

Thyroid volumes in schoolchildren of the Emirates.

Iodine deficiency is a major public health problem, an enlarged goiter being its most apparent manifestation. Recent studies have used US as an accurate and precise method of measuring thyroid size. The aim of this study was to describe thyroid volumes measured by US among school-aged children in the United Arab Emirates. Cross-sectional studies were performed in 4,381 school children, aged 6-17 yr in three locations in the Emirates. Data were collected on age, sex, weight, thyroid size by palpation and US, and urinary iodine. Age/sex and body surface area (BSA) upper limits of thyroid volume were derived. Median urinary iodine in Abu Dhabi, Al Ain and in rural areas of Dubai were 9.9, 12.0 and 9.6 mg/dl respectively. The goiter prevalence by palpation was 28.1%, 26.4% grade 1 and 1.7% grade 2. There was significant difference in median and upper limit of thyroid volumes between boys and girls (p < 0.001). The thyroid volumes of subjects, as assessed by US, progressively increased with age for both sexes (r = 0.53, p < 0.001). In schoolchildren in the Emirates, the best predictors of thyroid volume were BSA, height and weight. The thyroid volumes of the children in this study appear comparable with those reported in a European survey in 1997.

Thyroid volumes in schoolchildren of Tehran: comparison with European schoolchildren.

Since the normative values of thyroid volume ultrasonography results from European schoolchildren were endorsed by the World Health Organization (WHO), few studies have addressed the limitation of the recommended references as universal normative values for thyroid volume. Our objective was to describe thyroid volume measured by ultrasonography in Tehranian schoolchildren and compare them with the WHO normative values. Cross-sectional studies were performed in 2016 schoolchildren, aged 6-15 yr, in Tehran 10 yr after distribution of iodized salt. Data were collected on age, sex, weight, height, thyroid size by palpation and ultrasonography, and urinary iodine. Age/sex and body surface area (BSA) upper limits (97th percentile) of thyroid volume were derived. The goiter prevalence was 42% by palpation, 31% grade 1 and 11% grade 2. Median urinary iodine was 21.2 microg/dl. The 97th percentiles were comparable in girls and boys of all ages. Applying the WHO thyroid volume references to the Tehranian children, they did not show any enlarged thyroid based on BSA and on age, even in 11% of children with grade 2 (visible) goiter. In the Tehranian children, the best predictors of thyroid volume were BSA, height and weight. Using linear regression, the 97th percentile of thyroid volume from Tehranian children were lower than the corresponding references from the WHO normative values. The results indicate that a thyroid volume reference based on weight alone would perform as well as the one based on BSA. In addition, until the adoption of a new applicable international reference for thyroid volume, the use of local reference in the screening of children for thyroid enlargement is recommended.