Urinary iodine excretion in pregnant women residing in areas with adequate iodine intake

Iodized Salt May Not Be Sufficient to Guarantee an Adequate Iodine Intake in Pregnant Women

Adequate iodine intake is of crucial importance in pregnancy to meet the thyroid hormone needs of both mother and fetus. In the present study, undertaken as a part of the surveillance actions following the introduction in Italy of a national salt iodination program in 2005, the iodine intake was investigated in 123 pregnant women and 49 control women living in the same area of central Italy. All the participants were screened for urinary iodine concentration (UIC), serum level of thyrotropin, free-thyroxine, free-triiodothyronine, and thyroid volume. Moreover, they were provided with a questionnaire on the use of iodine-containing salt or supplements. Control women had a median UIC of 102 µg/L, consistent with an iodine sufficiency, while in pregnant women the median UIC value was 108 µg/L, lower than the endorsed UIC of 150 µg/L. In addition, pregnant women showed a significantly increased median thyroid volume compared to controls. Interestingly, the median UIC did not differ between pregnant women not using iodine-containing salt or supplements and those regularly consuming iodized salt alone, while pregnant women with a daily intake of iodine-containing supplements had an adequate median UIC (168 µg/L). In conclusion, the data reported here showed that pregnant women and their fetuses are still exposed to the detrimental effects of iodine deficiency and that the consumption of iodine-containing supplements should be recommended in pregnancy.

Sustained Elimination of Iodine Deficiency Within the Third Decade After Compulsory Iodine Supplementation Policy in the South of Iran: A Population-Based Cross-Sectional Study

Objectives

Recently, some studies in Iran have shown mild to moderate iodine concentrations in adult and pregnant women populations despite iodine sufficiency in children. This study aimed to evaluate the urine iodine status and salt intake among adult households in the city of Sadra, Fars province in southern Iran, and to assess its possible influencing factors.

Method

Participant households for this cross-sectional study were selected using randomized cluster sampling in the city of Sadra, Fars province, southern Iran from 1 February, 2021 to 30 November, 2021. Two subjects >18 y of age from each household were invited. Ninety-two subjects (24 men, 68 women) were enrolled. The participants were asked to collect their 24 h urine. They were then examined for thyroid disorders and subjected to thyroid ultrasonography and thyroid function tests. Urine samples were tested for iodine, sodium, and creatinine concentrations. Household salt intake was also estimated.

Results

Median urine iodine content (UIC) in the participants was 175 (IQR: 117, 250) μg/L, whereas the median salt consumption per person per day was 9.6 (IQR, 7.3-14.5) g. Sex, methods of salt storage, presence of goiter or thyroid nodules, the addition of salt in the cooking stage, and subclinical hypothyroidism had no effect on UIC, whereas individuals with hypertension and lower education had significantly lower iodine concentrations. UIC had a significant positive correlation with urine sodium and thyroid stimulating hormones (TSH) concentrations (P < 0.001, 0.046) and a negative correlation with thyroid volume and T4 (P = 0.029, 0.018).

Conclusion

Iodine status in the adult population of Sadra city was categorized as sufficient, although the iodine concentrations reported in Tehran were insufficient. The contributing factor can be higher salt consumption or possible higher environmental iodine concentrations in Sadra city than Tehran.

Assessment of Iodofolic Supplementation on Thyroid Function in Pregnant Women with Iodine Sufficient Status and their Infants in Birjand

BACKGROUND

Maintaining iodine at sufficient levels is necessary throughout the pregnancy to prevent adverse outcomes in infants. This study aimed to assess iodofolic supplementation's impact on thyroid function in women at the end of the third trimesters of gestation.

METHODS

This case-control study was conducted on 130 pregnant women in the Birjand, east of Iran, during the period from August 2017 to February 2019. We assessed iodofolic supplementation effect in the women at the first trimesters of gestation and followed them at the end of the third trimesters and also their infants on days 3-5. Serum samples were obtained from women and infants for measuring levels of thyroid-stimulating hormone (TSH). Urinary iodine concentration (UIC) was also determined at the end of the third trimester.

RESULTS

The median serum TSH concentration in the folic acid consumed group (3.26 ± 1.91) did not significantly differ from another group (2.98 ± 1.41), (p = 0.68). There is also no considerable difference in the mean serum TSH concentration between infants born from mothers who consumed folic acid in the first trimester of pregnancy and another group (p = 0.50). The TSH concentration in all infants was below 5 μM/L. The significant difference in the mean of UIC was also not observed between pregnant women in the folic acid consumed group (188.02 ± 105.38) and iodofolic consumed group (225.77 ± 130.26), (p = 0.13).

CONCLUSION

Iodine intake in our study was sufficient according to the WHO recommendation and idofolic supplementation was not emphasized.

Trend of Iodine Status in the Eastern Mediterranean Region and Impact of the Universal Salt Iodization Programs: a Narrative Review

Recognizing the importance of iodine deficiency as a single most important preventable cause of brain damage, World Health Organization (WHO) urged all countries to scale up salt iodization since 1991 where iodine deficiency was declared as a global public health problem. All countries committed to report on the national iodine status of school-aged children (6-12 years), every 3 years. This paper aims to evaluate the progress of countries in Eastern Mediterranean Region (EMR) toward the eradication of iodine deficiency disorders (IDD) and recommend operational action to support implementation of the WHO Regional Nutrition Strategy (2020-2030). Salt iodization in EMR has been scaled up with significant progress in increasing the proportion of dietary salt which is adequately iodized. As a result, many countries such as Qatar, Kuwait, Bahrain, Jordan, Oman, and Iran have achieved, or are now on the threshold of achieving IDD elimination. The WHO in coordination with United Nations Children's Fund is working with member states to ensure suitability of these achievements. Hence, efficient monitoring will help member states to measure the magnitude of IDD as a public health problem and to monitor the effects of the intervention on the iodine status of a population. Policy makers should take proactive steps to enforce mandatory regulatory measures for USI, through a multi-sectoral coordination, and careful assessments and estimates of iodine nutritional status. Coordination between the two national programs of USI and salt reduction intake is necessary.

The Clinical Value and Variation of Antithyroid Antibodies during Pregnancy

Antithyroid antibodies, which include thyroid-stimulating hormone receptor antibodies (TRAbs), thyroid peroxidase antibodies (TPOAbs), and thyroid globulin antibodies (TgAbs), are widely known for their tight association with thyroid autoimmune diseases. The variation in all three kinds of antibodies also showed different trends during and after pregnancy (Weetman, 2010). This article reviewed the the physiological changes, while focusing on the variation of thyroid antibodies concentration in women during and after pregnancy, and adverse consequences related to their elevation. Since abnormal elevations of these antithyroid antibodies may lead to adverse outcomes in both mothers and fetuses, special attention must be paid to the titer of the antibodies during pregnancy. The molecular mechanisms of the variations in those antibodies have yet to be explained. The frequency and timing of thyroid antibody measurement, as well as different reference levels, also remain to be elucidated.

Thyroid volume and nodular and diffuse thyroid diseases by ultrasonography in pregnant women: A case-control study

Background

Currently, it is shown that pregnancy may have an impact on the thyroid that can be leading to pregnancy complications such as abortion, preeclampsia, and preterm delivery. The objective was to compare the thyroid volume, number and characteristics of thyroid nodules, and prevalence of diffuse thyroid diseases in a sample of Iranian pregnant women in the first trimester to nonpregnant women.

Materials and Methods

This case-control study was conducted on 298 pregnant and 290 nonpregnant women. Thyroid volume, maximum diameter of thyroid nodules and prevalence of moderate to highly suspicious thyroid nodules, Hashimoto's appearance and goiter were assessed using thyroid ultrasonography. Antithyroperoxidase (TPO) antibodies were measured if the sonographic features were highly suggested for Hashimoto's thyroiditis.

Results

The mean of total thyroid volume in pregnant and nonpregnant women was 6 and 6.5 ml, respectively (P = 0.053), and the median (interquartile range) was 6.2 and 5.5, respectively. Nodules were observed in 16.4% of pregnant and 16.6% of nonpregnant women (P = 0.845). Hashimoto's thyroiditis was detected in 6.7% of pregnant and 12.4% of nonpregnant women (P = 0.013). Anti-TPO antibodies were detected in 5% of pregnant and 9.3% of nonpregnant women (P = 0.034).

Conclusion

The thyroid volume and nodule characteristics in the first trimester of pregnancy were similar to nonpregnant women. Hashimoto's thyroiditis and anti-TPO antibodies in pregnant women were significantly lower than in nonpregnant women.

Iodine Nutrition and Thyroid Function in Pregnant Women Exposed to Different Iodine Sources

Pregnant women are more vulnerable to iodine deficiency and iodine excess. The study aimed to assess the changes in iodine nutrition and thyroid function of pregnant women exposed to different iodine sources resulting in various iodine intakes during pregnancy. From 2016 to 2017, 2004 healthy pregnant women aged 20-35 years from Shandong and Tianjin, China, were enrolled. Urinary iodine concentration (UIC), drinking water iodine content (WIC), thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroid hormone (FT4), thyroglobulin (Tg), serum thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured. Pregnant women in both Shandong and Tianjin were iodine sufficient, but the median UIC in pregnant women was significantly higher in Shandong (244 μg/L) than that in Tianjin (159 μg/L). No differences were found in UIC over the course of gestation in Shandong. In Tianjin, the UIC decreased during 13-24 weeks and stabilized thereafter. Compared with Tianjin, TSH levels were higher and FT3 and FT4 levels were lower in Shandong. Both FT3 and FT4 significantly decreased during pregnancy in Shandong and Tianjin. TSH and Tg increased over the course of gestation in both Shandong and Tianjin. The iodine status of pregnant women in Tianjin and Shandong were sufficient, but different changing patterns in UIC and thyroid function during pregnancy were presented. More attention should be focused on iodine nutrition of pregnant women, even in iodine-sufficient areas.

A 7-year study on the prevalence of congenital hypothyroidism in northern Iran

Background

Congenital hypothyroidism (CH) is one of the most common congenital endocrine disorders.

The present study determined the prevalence and demographic characteristics of congenital hypothyroidism in the north of Iran.

Objective

To determine the prevalence of congenital hypothyroidism based on transient and permanent types with demographic characteristics in Mazandaran province in northern Iran.

Methods

This retrospective descriptive survey analyzed the medical records of children with primary diagnosis of CH in health centers in all cities of Mazandaran Province between June 2009 and March 2016. To compare the study groups (CH type) in terms of quantitative and qualitative variables, the t-test and Chi-square test were used, respectively using the SPSS22. P-value <0.05 was considered as significant.

Results

Of 269,088 infants screened during the study period, 548 infants with primary congenital hypothyroidism were identified (a prevalence of 1 per 491 births) and congenital hypothyroidism was definitively diagnosed in 389 children (a prevalence of 1 per 453 births); of them, 169 had permanent CH (a prevalence of 1 per 1043 births) and 220 had transient CH (a prevalence of 1 per 801 births). The female to male ratio in the permanent congenital hypothyroidism group was higher than that in the transient congenital hypothyroidism group (p=0.08). The family relationship between mother and father was stronger in the permanent congenital hypothyroidism group than in the transient congenital hypothyroidism group (p=0.03).

Conclusion

These findings show that congenital hypothyroidism is more prevalent in the north of Iran than in other areas of Iran; the prevalence of transient CH is particularly higher than permanent CH.

Iodine deficiency in pregnancy: Still a health issue for the women of Cassino city, Italy

OBJECTIVE

The World Health Organization, the United Nations Children's Fund, and the International Council for the Control of Iodine Deficiency Disorders recommend a median urinary iodine concentration (UIC) in pregnant women between 150 µg/L and 249 µg/L. In the present study, we evaluated whether in the urban area of Cassino (central Italy), after a national salt iodination program (30 mg/kg) was introduced in 2005, the increased demand of iodine during pregnancy was satisfied.

METHODS

Between January 2016 and April 2017, 99 pregnant women were enrolled to evaluate UIC in spot urine samples, serum level of thyrotropin, free thyroxine, antithyroglobulin and antithyroperoxidase autoantibodies, and thyroid volume by ultrasonography. Eighty clinically healthy non-pregnant women were evaluated as controls.

RESULTS

The median UIC was of 97.7 µg/L and 110.3 µg/L, respectively, in control and pregnant women. A significant increase (P < 0.001) of median thyroid volume was found in pregnant women, relative to control women, being, respectively, 10.4 mL (range 3.68-19.49 mL) and 7.16 mL (range 2.57-14.00 mL). A positive correlation was found between thyroid volume and anthropometric parameters, and an inverse correlation was identified between free thyroxine serum levels and anthropometric parameters.

CONCLUSIONS

This observational study found that the majority of pregnant women and their fetuses appear not to be protected from the detrimental consequences of iodine deficiency. Therefore, the identification of new strategies to increase the knowledge and awareness of the general population regarding the beneficial effects of iodine supplementation during pregnancy is highly required.

Thyroid volume and serum calcitonin changes during pregnancy

BACKGROUND

Pregnancy has a profound impact on thyroid homeostasis which results in change of thyroid function and thyroid volume (TV). Moreover, calcitonin (CT), and its gene-related peptide have been demonstrated to play an important role in the implantation process.

PURPOSE

To evaluate changes in TV and serum CT levels during pregnancy.

METHODS

One hundred and fifty-five pregnant women were consecutively enrolled at the first trimester of gestation and underwent clinical, biochemical and sonographic assessment at enrollment, at the second and third trimesters and at 6 months after delivery.

RESULTS

Throughout gestation serum TSH exceeded the upper specific first trimester cut-off in 5% of patients. TV significantly increased at the third trimester of gestation and returned to baseline levels at 6 months after delivery, while serum CT levels did not show significant changes. TV directly correlated with BMI or gestational weight gain at each trimester of pregnancy, while no significant association between serum CT levels and either weight or TV were found. Finally, in none of the patients with nodular goiter an increase in the volume of the nodules was noted. The appearance of a nodule was recorded during the second trimester in one patient.

CONCLUSION

This study confirms a prevalence of thyroid autoimmunity/hypertropinemia in 3-5% of pregnant women and shows that serum CT does not change in relation to the transient increase in TV occurring during gestation. An adequate daily iodine supplementation might be particularly useful during pregnancy to limit the TSH increase and the resulting thyroid gland and nodule enlargement.

Incidence of thyroid dysfunction in an Iranian adult population: the predictor role of thyroid autoantibodies: results from a prospective population-based cohort study

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.

Iodine supplementation for women during the preconception, pregnancy and postpartum period

BACKGROUND

Iodine is an essential nutrient required for the biosynthesis of thyroid hormones, which are responsible for regulating growth, development and metabolism. Iodine requirements increase substantially during pregnancy and breastfeeding. If requirements are not met during these periods, the production of thyroid hormones may decrease and be inadequate for maternal, fetal and infant needs. The provision of iodine supplements may help meet the increased iodine needs during pregnancy and the postpartum period and prevent or correct iodine deficiency and its consequences.

OBJECTIVES

To assess the benefits and harms of supplementation with iodine, alone or in combination with other vitamins and minerals, for women in the preconceptional, pregnancy or postpartum period on their and their children's outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (14 November 2016), and the WHO International Clinical Trials Registry Platform (ICTRP) (17 November 2016), contacted experts in the field and searched the reference lists of retrieved studies and other relevant papers.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials with randomisation at either the individual or cluster level comparing injected or oral iodine supplementation (such as tablets, capsules, drops) during preconception, pregnancy or the postpartum period irrespective of iodine compound, dose, frequency or duration.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, risk of bias, extracted data and conducted checks for accuracy. We used the GRADE approach to assess the quality of the evidence for primary outcomes.We anticipated high heterogeneity among trials, and we pooled trial results using random-effects models and were cautious in our interpretation of the pooled results.

MAIN RESULTS

We included 14 studies and excluded 48 studies. We identified five ongoing or unpublished studies and two studies are awaiting classification. Eleven trials involving over 2700 women contributed data for the comparisons in this review (in three trials, the primary or secondary outcomes were not reported). Maternal primary outcomesIodine supplementation decreased the likelihood of the adverse effect of postpartum hyperthyroidism by 68% (average risk ratio (RR) 0.32; 95% confidence interval (CI) 0.11 to 0.91, three trials in mild to moderate iodine deficiency settings, 543 women, no statistical heterogeneity, low-quality evidence) and increased the likelihood of the adverse effect of digestive intolerance in pregnancy by 15 times (average RR 15.33; 95% CI 2.07 to 113.70, one trial in a mild-deficiency setting, 76 women, very low-quality evidence).There were no clear differences between groups for hypothyroidism in pregnancy or postpartum (pregnancy: average RR 1.90; 95% CI 0.57 to 6.38, one trial, 365 women, low-quality evidence, and postpartum: average RR 0.44; 95% CI 0.06 to 3.42, three trials, 540 women, no statistical heterogeneity, low-quality evidence), preterm birth (average RR 0.71; 95% CI 0.30 to 1.66, two trials, 376 women, statistical heterogeneity, low-quality evidence) or the maternal adverse effects of elevated thyroid peroxidase antibodies (TPO-ab) in pregnancy or postpartum (average RR 0.95; 95% CI 0.44 to 2.07, one trial, 359 women, low-quality evidence, average RR 1.01; 95% CI 0.78 to 1.30, three trials, 397 women, no statistical heterogeneity, low-quality evidence), or hyperthyroidism in pregnancy (average RR 1.90; 95% CI 0.57 to 6.38, one trial, 365 women, low-quality evidence). All of the trials contributing data to these outcomes took place in settings with mild to moderate iodine deficiency. Infant/child primary outcomesCompared with those who did not receive iodine, those who received iodine supplements had a 34% lower likelihood of perinatal mortality, however this difference was not statistically significant (average RR 0.66; 95% CI 0.42 to 1.03, two trials, 457 assessments, low-quality evidence). All of the perinatal deaths occurred in one trial conducted in a severely iodine-deficient setting. There were no clear differences between groups for low birthweight (average RR 0.56; 95% CI 0.26 to 1.23, two trials, 377 infants, no statistical heterogeneity, low-quality evidence), neonatal hypothyroidism/elevated thyroid-stimulating hormone (TSH) (average RR 0.58; 95% CI 0.11 to 3.12, two trials, 260 infants, very low-quality evidence) or the adverse effect of elevated neonatal thyroid peroxidase antibodies (TPO-ab) (average RR 0.61; 95% CI 0.07 to 5.70, one trial, 108 infants, very low-quality evidence). All of the trials contributing data to these outcomes took place in areas with mild to moderate iodine deficiency. No trials reported on hypothyroidism/elevated TSH or any adverse effect beyond the neonatal period.

AUTHORS' CONCLUSIONS

There were insufficient data to reach any meaningful conclusions on the benefits and harms of routine iodine supplementation in women before, during or after pregnancy. The available evidence suggested that iodine supplementation decreases the likelihood of postpartum hyperthyroidism and increases the likelihood of the adverse effect of digestive intolerance in pregnancy - both considered potential adverse effects. We considered evidence for these outcomes low or very low quality, however, because of study design limitations and wide confidence intervals. In addition, due to the small number of trials and included women in our meta-analyses, these findings must be interpreted with caution. There were no clear effects on other important maternal or child outcomes though these findings must also be interpreted cautiously due to limited data and low-quality trials. Additionally, almost all of the evidence came from settings with mild or moderate iodine deficiency and therefore may not be applicable to settings with severe deficiency.More high-quality randomised controlled trials are needed on iodine supplementation before, during and after pregnancy on maternal and infant/child outcomes. However, it may be unethical to compare iodine to placebo or no treatment in severe deficiency settings. Trials may also be unfeasible in settings where pregnant and lactating women commonly take prenatal supplements with iodine. Information is needed on optimal timing of initiation as well as supplementation regimen and dose. Future trials should consider the outcomes in this review and follow children beyond the neonatal period. Future trials should employ adequate sample sizes, assess potential adverse effects (including the nature and extent of digestive intolerance), and be reported in a way that allows assessment of risk of bias, full data extraction and analysis by the subgroups specified in this review.

Influence of maternal thyroid hormones during gestation on fetal brain development

Thyroid hormones (THs) play an obligatory role in many fundamental processes underlying brain development and maturation. The developing embryo/fetus is dependent on maternal supply of TH. The fetal thyroid gland does not commence TH synthesis until mid gestation, and the adverse consequences of severe maternal TH deficiency on offspring neurodevelopment are well established. Recent evidence suggests that even more moderate forms of maternal thyroid dysfunction, particularly during early gestation, may have a long-lasting influence on child cognitive development and risk of neurodevelopmental disorders. Moreover, these observed alterations appear to be largely irreversible after birth. It is, therefore, important to gain a better understanding of the role of maternal thyroid dysfunction on offspring neurodevelopment in terms of the nature, magnitude, time-specificity, and context-specificity of its effects. With respect to the issue of context specificity, it is possible that maternal stress and stress-related biological processes during pregnancy may modulate maternal thyroid function. The possibility of an interaction between the thyroid and stress systems in the context of fetal brain development has, however, not been addressed to date. We begin this review with a brief overview of TH biology during pregnancy and a summary of the literature on its effect on the developing brain. Next, we consider and discuss whether and how processes related to maternal stress and stress biology may interact with and modify the effects of maternal thyroid function on offspring brain development. We synthesize several research areas and identify important knowledge gaps that may warrant further study. The scientific and public health relevance of this review relates to achieving a better understanding of the timing, mechanisms and contexts of thyroid programing of brain development, with implications for early identification of risk, primary prevention and intervention.

Urinary iodine and thyroid determinants in pregnancy: a follow up study in Sri Lanka

Background

Iodine deficiency and thyroid dysfunction during pregnancy is associated with number of adverse outcomes that includes mental and physical disabilities creating a huge human and economic burden in later life. Several indicators are used to assess the iodine status of a population: thyroid size by palpation and/or by ultrasonography, urinary iodine excretion and the blood thyroid hormone profile.

Methods

This prospective study was designed to assess the iodine nutrition during the course of pregnancy with reference to urine iodine concentration (UIC) and thyroid determinants among 425 pregnant women from Galle district, Sri Lanka. UIC was estimated in all three trimesters and thyroid functions were assessed in first and third trimesters.

Results

Median (inter-quartile range IQR) UIC was 170.9 (100.0–261.10) μg/L, 123.80 (73.50–189.50) μg/L and 105.95 (67.00–153.50) μg/L in the first, second and third trimesters respectively (p < 0.001). Median thyroid stimulating hormone (TSH) level in the first trimester was 1.30 (0.80–1.80) µIU/mL. This value significantly increased (p < 0.001) to 1.60 (1.20–2.10) µIU/mL at the 3^rd trimester even though it was maintained within the reference range (0.3 – 5.2 µIU/mL). In the assessment of thyroid gland, 67 (16.0 %) women had palpable or visible goitres and 55 (13.1 %) had a goitre that was palpable but not visible. The median thyroid volume of the sample was 5.16 mL (4.30; 6.10 mL) as measured by ultra sound (US) scanning. In multiple regression analysis after controlling for other independent variables (anthropometric, demographic and biochemical parameters); initial body mass index (BMI), goitre size, thyroid volume and parity had significant correlations with the third trimester urinary iodine levels. The thyroid volume accounted for 4.5 % of the urinary iodine variation.

Conclusions

Even though iodine status was progressively worsening with the advancement of pregnancy and iodized salt consumption has not met with the increasing demand for iodine, it was not reflected in the serum TSH level. Therefore, it is worthwhile to assess the long term effects of rising TSH levels and inadequate iodine nutrition during pregnancy on the offspring to prevent even mild iodine deficiency.

Iodine deficiency in pregnant women in Austria

BACKGROUND/OBJECTIVES

In Austria, iodine deficiency has been considered to be eliminated owing to table salt fortification with iodine, but whether this also applies to pregnant women is unclear. Even mild iodine deficiency during gestation may lead to neurocognitive sequelae in the offspring.

SUBJECTS/METHODS

This is a cross-sectional investigation of urinary iodine excretion in 246 pregnant women (first trimester n=2, second trimester n=53, third trimester n=191, gestational diabetes mellitus n=115, no gestational diabetes mellitus n=131). The iodine content of morning spot urine samples was determined using inductively coupled plasma mass spectrometry.

RESULTS

Pregnant women in the Vienna area had a median urinary iodine concentration (UIC) of 87 μg/l. Only 13.8% of the cohort were in the recommended range of 150-249 μg/l, whereas 21.5% had a UIC of 0-49 μg/l, 40.2% had a UIC of 50-99 μg/l and 19.5% had a UIC of 100-149 μg/l. In all, 4.9% had a UIC over 250 μg/l. A total of 137 women of foreign origin had a significantly higher iodine excretion compared with Austrian-born women. Maternal or gestational age had no influence on UIC. Although 79 women on iodine supplementation had a significantly higher iodine concentration compared with women without iodine supplementation (97.3 vs 80.1 μg/l, P=0,006), their UIC was below the recommended range, indicating that doses of 100-150 μg per day are not sufficient to normalize iodine excretion. Sodium and iodine concentrations in the urine were tightly correlated (R=0.539, n=61), suggesting that low intake of iodized salt might contribute to insufficient iodine supply.

CONCLUSIONS

This study shows that pregnant women in the Vienna area have a potentially clinically significant iodine deficiency and that currently recommended doses of iodine supplementation may not be sufficient.

Alterations of thyroid volume and nodular size during and after pregnancy in a severe iodine-deficient area

OBJECTIVE

The effects of pregnancy on thyroid nodules were investigated in a few number of studies. We aimed to evaluate the prevalence of thyroid nodules, the changes in size, volume and number of nodules during pregnancy and after delivery in pregnant women.

DESIGN AND METHODS

This prospective study was performed in a severe iodine-deficient area and included 83 pregnant women (mean age 30·4 ± 5·5 years). We evaluated thyroid hormone levels, ultrasound examination of thyroid and urine iodine concentration (UIE) at each trimester and at 3-month post-partum period (PP). All patients with thyroid nodules >1 cm underwent fine-needle aspiration biopsy (FNAB) after the last visit at the PP.

RESULTS

Twenty-six women had thyroid nodules on thyroid ultrasonography at the first trimester. The volume of single/dominant nodule showed enlargement during pregnancy and remained at the PP; however, it was not significant (first trimester: 0·83 ± 0·8 ml; second trimester: 0·92 ± 1 ml; third trimester: 0·99 ± 1·2 ml; PP: 0·92 ± 1·2 ml). The maximum diameter of single/dominant nodule in the third trimester of pregnancy (12·6 ± 5·4 mm) was greater than the first trimester (11·9 ± 4·8 mm) (P = 0·002). The number of nodules did not change during pregnancy. The mean TV increased during pregnancy and remained 3 months after delivery (P < 0·001), and the maximum value of TV was reached in the third trimester (14·2 ± 7·9 ml). FNAB results revealed a 6·6% prevalence of malignancy among the nodules.

CONCLUSIONS

Thyroid nodules were present in 30·1% of pregnant women. While size of the single/dominant thyroid nodule increased significantly during pregnancy, the number of nodules did not change.

An evo-devo approach to thyroid hormones in cerebral and cerebellar cortical development: etiological implications for autism

The morphological alterations of cortical lamination observed in mouse models of developmental hypothyroidism prompted the recognition that these experimental changes resembled the brain lesions of children with autism; this led to recent studies showing that maternal thyroid hormone deficiency increases fourfold the risk of autism spectrum disorders (ASD), offering for the first time the possibility of prevention of some forms of ASD. For ethical reasons, the role of thyroid hormones on brain development is currently studied using animal models, usually mice and rats. Although mammals have in common many basic developmental principles regulating brain development, as well as fundamental basic mechanisms that are controlled by similar metabolic pathway activated genes, there are also important differences. For instance, the rodent cerebral cortex is basically a primary cortex, whereas the primary sensory areas in humans account for a very small surface in the cerebral cortex when compared to the associative and frontal areas that are more extensive. Associative and frontal areas in humans are involved in many neurological disorders, including ASD, attention deficit-hyperactive disorder, and dyslexia, among others. Therefore, an evo-devo approach to neocortical evolution among species is fundamental to understand not only the role of thyroid hormones and environmental thyroid disruptors on evolution, development, and organization of the cerebral cortex in mammals but also their role in neurological diseases associated to thyroid dysfunction.

Variations of urinary iodine during the first trimester of pregnancy in an iodine-replete area. Comparison with non-pregnant women

OBJECTIVE

To assess variations of urinary iodine concentration (UIC) during a 4-week period among pregnant and non-pregnant women in an iodine-replete area.

DESIGN

Pregnant (in their first trimester of pregnancy) and non-pregnant women referred to two maternity hospitals in Tehran were consecutively recruited from September 2005 to March 2006. Urine samples (5-10 mL) were collected on an every-other-day basis for 4 weeks (i.e., 12 samples for each individual). UIC was determined using a modified Sandell-Kolthoff method.

RESULTS

Thirty-six pregnant and 32 non-pregnant women completed the study. Mean±SD age of pregnant women was 27.4±6.4 and of non-pregnant women 27.6±4.5 years (P=0.897). Mean±SD gestational age was 11±3.3 weeks in pregnant participants. Median UIC of <100, 100-149, 150-249, and ≥250 µg/L was present in 19.4, 25, 30.6, and 25% of pregnant, 15.6, 37.5, 34.4, and 12.5% of non-pregnant, and 17.6, 30.9, 32.4, and 19.1% of total individuals, respectively. Median UIC values of samples numbers 1 to 12 were not significantly different either in pregnant (P=0.591) or in non-pregnant subjects (P=0.745). Except for sample number 11, median UIC was not significantly different between pregnant versus non-pregnant women (P values >0.05). Mean SD values for UIC in samples numbers 1 to 12 in pregnant women was 138.4 (24.1-404) and in non-pregnant women 118 (29.5-272.4) µg/L (P=0.286).

CONCLUSION

There was a wide intrapersonal variation in UIC values among pregnant and non-pregnant women residing in an iodine-replete area, supporting the notion that casual UIC would not reflect the iodine status of the individual.

Nutritional Iodine Status in Gestation and its Relation to Geographic Features in Urmia County of Northwest Iran

Background

Iodine is an important component for the proper function of the thyroid and fetal development.

Objective

To evaluate the influence of geographic variation on nutritional iodine status during pregnancy.

Methods

Four hundred eighty-nine women in the first trimester of pregnancy were enrolled. Of these, 419 (85.5%) were from the plain districts and 70 (14.5%) from mountainous regions. Data were obtained on demographic characteristics and accessibility of iodized salt, and samples of table salt were collected. In the third trimester, 322 women remained in the study: 281 (87.2%) from the plains and 41 (12.8%) from the mountainous regions. Salt and urine samples were analyzed for iodine content.

Results

All participants stated that they used iodized table salt. The proportion of salt samples with optimal iodine content (30 ppm) from the plains and mountain regions were 68.7% and 88%, respectively. The median urinary iodine content (UIC) in the plains area in the first and third trimesters was 82 and 119 μg/L, respectively. The corresponding values in the mountain region were 34.5 μg/L and 76 μg/L. The prevalence of subjects with an inadequate iodine intake (UIC < 150 μg/L) in first and third trimester in the plains and mountain regions were 84.5% and 66.9% vs 98.6% and 90.2%, respectively.

Conclusions

The prevalence of pregnant women exhibiting UIC < 150 μg/L in the mountain region was substantially higher than those in the plain district. Our findings also show that the current strategy for eradication of iodine deficiency in school-aged children would not fulfill iodine requirements in pregnancy and that additional source(s) of iodine are required to prevent the adverse effects of iodine deficiency in pregnancy. Further studies are needed to address the cause(s) for the rapid depletion of iodine stores in pregnancy.

Urine iodine levels in preeclamptic and normal pregnant women

The aim of this study was to investigate the urine iodine concentration in women with severe preeclampsia and in healthy women in Erzurum, Turkey. Urine specimens were obtained from 40 severe preeclampsia and 18 healthy pregnant women. Urinary iodine levels were determined by the Foss method based on the Sandell-Kolthoff reaction. The urinary iodine level for women with severe preeclampsia was 4.25 +/- 2.7 microg/dL, lower than 20.89 +/- 6.4 microg/dL of urinary iodine for healthy pregnant women (p < 0.001). Blood magnesium concentration was found to be 1.63 +/- 0.05 mg/dL for women with severe preeclampsia, which is lower than that of healthy pregnant women (1.87 +/- 0.05 mg/dL; p < 0.001). There was a positive correlation between urinary iodine level and blood magnesium level in pregnant women with preeclampsia (Pearson correlation coefficient = 0.43; p < 0.01). However, there was no correlation between urinary iodine level and blood magnesium level in healthy pregnant women. There was no difference in thyroid hormone levels (T4, TSH, FT4) between women with severe preeclampsia and healthy pregnant women. However, there was a difference in T3 thyroid hormone levels between women with severe preeclampsia (1.86 +/- 0.4 microg/dL) and healthy pregnant women (1.45 +/- 0.3 microg/dL; p < 0.001). There was also a difference in FT3 between women with severe preeclampsia (2.77 +/- 0.4 pg/mL) and healthy pregnant women (2.41 +/- 0.5 microg/dL; p < 0.01). Urinary iodine excretion is currently the most convenient laboratory marker of iodine deficiency. The method is useful for the rapid and low-cost assessment of iodine deficiency. Our results suggested that urinary iodine concentration might be a useful marker for prediagnosing preeclamptic women. In addition, iodine supplementation may also be considered for preeclamptic therapy.

Hypothyroxinemia: a subclinical condition affecting neurodevelopment

Hypothyroxinemia with low levels of circulating free thyroxine and normal levels of thyrotropin, which is usually caused by iodine deficiency, may affect pregnant women even in apparently iodine-sufficient areas, and it is debated whether it increases the risk of neurodevelopmental abnormalities in children born to them. Epidemiological observations indeed indicate that this is the case. Animal models show abnormal brain cortical cytoarchitecture in pups born to mildly hypothyroxinemic dams. In regions where the availability and use of iodized salt is inadequate (where <90% of households use iodized salt), the WHO and the International Council for Control of Iodine Deficiency Disorders (ICCIDD) recommend iodine supplementation so that the total iodine intake is 250 µg/day to prevent iodine deficiency during gestation and lactation.

Delayed neurobehavioral development in children born to pregnant women with mild hypothyroxinemia during the first month of gestation: the importance of early iodine supplementation

BACKGROUND

Maternal hypothyroxinemia, due to gestational iodine deficiency, causes neurological dysfunctions in the progeny. Our aim was to determine the effects of delayed iodine supplementation (200 microg KI per day) to mildly hypothyroxinemic pregnant women at the beginning of gestation (i.e., having circulating free thyroxine [FT(4)] within the 0th-10th percentile interval and normal thyrotropin [TSH]) on the neurobehavioral development of their children.

METHODS

Using the Brunet-Lézine scale, we evaluated the neurocognitive performance at 18 months of age in three groups of children. Group 1 included children of women with FT(4) above the 20th percentile at 4-6 gestational weeks and at full-term. Group 2 included children of mildly hypothyroxinemic women diagnosed during the first 12-14 gestational weeks and with FT(4) above the 20th percentile at full-term. Group 3 included children born to mildly hypothyroxinemic women at full-term, without iodine supplementation during gestation. Women of all groups were iodine supplemented from the day of enrollment until the end of lactation.

RESULTS

Before iodine supplementation, 33.0% of the women (114 out of 345) were hypothyroxinemic, with FT(4) below normal in 28 of them (8.1%). None were found to be hypothyroxinemic at full-term after supplementation. The mean (+/-SD) developmental quotient of children was 101.8 +/- 9.7 in group 1 (n = 13) vs. 87.5 +/- 8.9 in group 3 (n = 19; p < 0.001) and 92.2 +/- 5.4 in group 2 (n = 12; p < 0.05). The difference between groups 2 and 3 was not statistically significant. Delayed neurobehavioral performance was observed in 36.8% and 25.0% of children in groups 3 and 2, respectively, compared with no children in group 1. Differences (p < 0.001) were found on gross and fine motor coordination and socialization quotients. No statistically significant differences were found on language quotients.

CONCLUSIONS

A delay of 6-10 weeks in iodine supplementation of hypothyroxinemic mothers at the beginning of gestation increases the risk of neurodevelopmental delay in the progeny. Public health programs should address the growing problem of iodine deficiency among women of gestational age in developing and industrialized nations.

Iodine and magnesium levels in maternal and umbilical cord blood of preeclamptic and normal pregnant women

The objective of this study was to investigate the relationship between preeclampsia and iodine levels and magnesium concentration in the blood of subjects in the northeast Anatolia region where iodine deficiency is common. Blood specimens were obtained from 24 preeclamptic and 16 healthy pregnant women. Iodine levels in blood were determined by the Foss method based on the Sandell-Kolthoff reaction. Serum protein-bound iodine (PBI) levels and magnesium concentration in maternal blood were lower in patients with severe preeclampsia compared to normal pregnant women (8.46 +/- 1.22 vs. 11.46 +/- 1.71 microg/dL, p < 0.001, 1.63 +/- 0.05 vs. 1.86 +/- 0.05 mg/dL, p < 0.001, respectively). Serum PBI levels and magnesium concentration in umbilical cord blood were higher in patients with severe preeclampsia than in normal pregnant women (8.84 +/- 1.9 vs. 7.33 +/- 1.07 microg/dL, p < 0.05, 2.48 +/- 0.03 vs. 2.02 +/- 0.01 mg/dL, p < 0.001, respectively). There was a positive correlation between the serum PBI levels in maternal blood and magnesium concentration in maternal blood in patients with severe preeclampsia (r = 0.41, p < 0.05). Thus, iodine may be one factor contributing to the pathophysiology of preeclampsia. Iodine supplementation may be effective therapy in preeclamptic in pregnant women.

Iodine requirements during pregnancy, lactation and the neonatal period and indicators of optimal iodine nutrition

OBJECTIVE

This paper re-evaluates the requirements for iodine during pregnancy, lactation and the neonatal period, and formulates original proposals for the median concentrations of urinary iodine (UI) that indicate optimal iodine nutrition during these three critical periods of life. This paper also discusses the measurements that are used to explore thyroid functions during the same periods.

DESIGN

An extensive and critical review of the literature on thyroid physiopathology during the perinatal period.

SETTING

Human studies conducted in various regions throughout the world.

SUBJECTS

Pregnant women, lactating women, and newborns.

RESULTS

The following proposals are made after extensive review of the literature: the requirement for iodine by the mother during pregnancy is 250-300 microg day-1; during lactation the requirement is 225-350 microg day-1; and during the neonatal period the requirement of the infant is 90 microg day-1. The median UI that indicates an optimal iodine nutrition during these three periods should be in the range of 150-230 microg day-1. These figures are higher than recommended to date by the international agencies.

CONCLUSIONS

Pregnant women and young infants, but especially the second group, are more sensitive to the effects of an iodine deficiency (ID) than the general population because their serum thyroid-stimulating hormone (TSH) and thyroxine are increased and decreased, respectively, for degrees of ID that do not seem to affect thyroid function in the general population. Systematic neonatal thyroid screening using primary TSH could be the most sensitive indicator to monitor the process of ID control.

Iodine nutrition in pregnancy and lactation in Iran

Objective: To describe studies evaluating urinary iodine excretion during pregnancy and lactation in women living in cities with adequate or more than adequate iodine intake.

Design: Cross-sectional study conducted between 1996 and 1998 in pregnant women and a study of lactating women conducted in 2003.

Settings and Subjects: Pregnant women attending prenatal clinics in four cities in the Islamic Republic of Iran. Urinary iodine excretion and thyroid volume was measured in 403 women. In a second study, 100 lactating women from Taleghani Hospital in Gorgan, Iran were evaluated for thyroid size, and both urinary and breast milk iodine concentrations were determined.

Results: In Rasht city, 84% of pregnant women had a urinary iodine concentration of ≥ 200 μg l-1, while in the other cities this percentage ranged from 45 to 55%. When data were combined for the cities of Ilam, Isfahan and Tehran, where women have an adequate or more than adequate median urinary iodine concentration, 51% of pregnant women had a urinary iodine concentration less than that recommended during pregnancy. In Rasht, where the median urinary iodine concentration indicates an excessive iodine intake, 15.4% of pregnant women had a urinary iodine concentration < 200 μg l-1. The mean urinary iodine concentration in lactating women was 250 μg l-1, and 16% of women had a urinary iodine concentration < 100 μg l-1. Grade 1 goitre was present in 8% of lactating women, and another 8% had grade 2 goitre.

Conclusions: Findings of this study call for further attention to iodine intake during pregnancy and lactation. The currently recommended intake of iodine through universal salt iodisation may not be adequate for pregnant and lactating women, and supplementation during pregnancy and lactation should be further considered in light of the latest recommendations.

Iodine status among pregnant women in Kuwait

Up to now, little has been known about iodine intake and the prevalence of iodine deficiency (ID), if any, in Kuwait. Urinary iodine excretion (UIE) and changes in thyroid function during pregnancy were thus evaluated.

METHODS

Urinary iodide level was measured in random urine samples collected from 326 pregnant women at different gestational trimesters. Blood samples were drawn for free T4 (FT4) and TSH level determination.

RESULTS

Median UIE levels fall within the normal range during all gestational trimesters i.e. >100 microg/l. However, if the new suggested recommendation for pregnant women <140 microg/l, is applied, median UIE values during trimesters 2 and 3 indicate ID. Mean serum TSH levels increased between trimesters 1 and 3 (p<0.05), whereas serum FT4 decreased between first and second trimesters (p<0.05), and this reduction continued at the third trimester. Furthermore, an increase in TSH levels for subjects with mild and moderate ID (Mi and Mo, respectively) were noticed (p<0.05) during the second trimester. However, FT4 levels dropped in subjects with Mi and Mo ID during the first trimester (p<0.05). In conclusion, these results suggest that 56.8% of pregnant women had median UIE level <145 microg/l, associated with high TSH and low FT4 levels.

CONCLUSION

Data obtained may indicate insufficient iodine intake among pregnant women in Kuwait.

Iodine supplementation during pregnancy: a public health challenge

Iodine deficiency remains the most frequent cause worldwide, after starvation, of preventable mental retardation in children. It causes maternal hypothyroxinemia, which affects pregnant women even in apparently iodine-sufficient areas, and often goes unnoticed because L-thyroxine (T4) levels remain within the normal range, and thyroid-stimulating hormone (TSH) is not increased. Even a mild hypothyroxinemia during pregnancy increases the risk of neurodevelopmental abnormalities, and experimental data clearly demonstrate that it damages the cortical cytoarchitecture of the fetal brain. The American Thyroid Association (ATA) recommends a supplement of 150 microg iodine/day during pregnancy and lactation, in addition to the use of iodized salt. We discuss the importance of iodine supplementation to ensure adequate T4 levels in all women who are considering conception and throughout pregnancy and lactation.

Assessment of intertrimester and seasonal variations of urinary iodine concentration during pregnancy in an iodine-replete area

OBJECTIVE

To assess intertrimester and seasonal variations in urinary iodine concentration (UIC) among pregnant women.

PATIENTS AND MEASUREMENTS

Pregnant Tehranian women, with no history of thyroid ablation or consumption of thyroid-affecting medication were selected consecutively from November 2004 to November 2006. Morning spot urine samples were collected from each participant during the first, second and third trimesters of pregnancy. Of 466 participants, 298 completed the study in all three trimesters of pregnancy. UIC < 150, 150-250, and > 250 microg/l indicated low, adequate, and high levels, respectively. UIC was measured using a modified Sandell-Kolthoff digestion method.

RESULTS

The pregnant women were aged 25.0 +/- 5.0 (range 16-48) years. Median UIC did not show seasonal fluctuations during pregnancy. However, median (range) UIC was 193 (19-840), 159 (16-640), and 141 (16-400) microg/l in the first, second and third trimesters of pregnancy, respectively (P < 0.0001). Frequency distributions of low, adequate and excessive UIC were 33.2, 31.2 and 35.6% in the first trimester, 46.0, 28.9 and 25.2% in the second trimester, and 53.4, 30.9 and 15.8% in the third trimester of pregnancy, respectively (P < 0.0001). Women with UIC < 150 were more frequently represented in the second vs. the first (P = 0.043; odds ratio 1.49, 95% confidence interval 1.012-2.213) and in the third vs. the first (P = 0.013; odds ratio 1.62, 95% confidence interval 1.108-2.379) trimesters of pregnancy than the 150-250 microg/l group were. UIC decreased throughout pregnancy in all seasons.

CONCLUSIONS

Iranian national salt iodization may prevent seasonal fluctuations of UIC but does not maintain median UIC within adequate and recommended ranges throughout pregnancy. Extra iodine supplementation during pregnancy is recommended.

Assessment of thyroid function and urinary and breast milk iodine concentrations in healthy newborns and their mothers in Tehran

OBJECTIVE

To measure breast milk iodine (MI) and urinary iodine (UI) concentrations in healthy newborns and their nursing mothers from an iodine-sufficient region to determine adequacy and to relate these parameters to thyroid function tests in mothers and infants.

DESIGN

Cross-sectional.

PATIENTS

Forty-eight healthy neonates of 37 to 42 weeks' gestation with normal cord blood TSH values and their mothers were recruited in Tehran, Iran.

MEASUREMENTS

Serum thyroid function tests were performed, and maternal and infant urinary iodine excretion, and maternal MI concentration were measured.

RESULTS

Neonatal age was 12.9 +/- 3.9 (mean +/- SD; range 7-30) days and maternal age was 25.8 +/- 5 years. Median (range) UI in neonates was 271 microg/l (57-800) and in mothers was 107 microg/l (20-710). Median (range) MI was 148 microg/l (45-750). Neonatal and maternal UI did not correlate with serum thyroid function tests. UI < 150, 150-230, and > 230 microg/l was found in 20, 12.5, and 67.5% of neonates and 79.1, 14, and 7% of mothers, respectively. MI was < 150, 150-180, and > 180 microg/l in 52.4, 11.9, and 35.7% of mothers, respectively.

CONCLUSIONS

Among euthyroid neonates, UI was adequate despite low median maternal UI and MI concentrations. There were no significant correlations between UI or MI and thyroid function tests in the mothers and infants.

Environmental perchlorate: why it matters

The only known mechanism of toxicity for perchlorate is interference with iodide uptake at the sodium-iodide symporter (NIS). The NIS translocates iodide across basolateral membranes to the thyroid gland so it can be used to form thyroid hormones (TH). NIS is also expressed in the mammary gland during lactation, so that iodide can be transferred from a mother to her child. Without adequate iodide, an infant cannot produce sufficient TH to meet its developmental needs. Effects expected from perchlorate are those that would be seen in conditions of hypothyroidism or hypothyroxinemia. The probability of a permanent adverse effect is greatest during early life, as successful neurodevelopment is TH-dependent. Study of perchlorate risk is complicated by a number of factors including thyroid status of the mother during gestation, thyroid status of the fetus, maternal and infant iodine intake, and exposure of each to other TH-disrupting chemicals. Perhaps the greatest standing issue, and the issue most relevant to the field of analytical chemistry, is the simple fact that human exposure has not been quantified. This review will summarize perchlorate's potential to adversely affect neurodevelopment. Whether current environmental exposures to perchlorate contribute to neuro-impairment is unknown. Risks posed by perchlorate must be considered in conjunction with iodine intake.

An assessment of urinary and breast milk iodine concentrations in lactating mothers from Gorgan, Iran, 2003

Dietary iodine is essential for the production of thyroid hormones. Breast-fed infants are reliant on maternal iodine intake. The aim of this study was to evaluate iodine sufficiency in lactating women in Iran. The sample consisted of 100 lactating mothers referred to the Taleghani Hospital of Gorgan, Iran. Goiter was graded according to World Health Organization (WHO) classification. Spot urine and breast-milk samples were collected for the measurement of iodine concentrations. Urine iodine concentrations (UIC) less than 100 and breast-milk iodine concentrations (MIC) less than 50 microg/L were considered consistent with iodine deficiency. Forty-three percent of women had grade 1 and 2 goiters, respectively. The median UIC was 259 microg/L. UIC was less than 100 in 16%. Grade 1 and 2 goiters were each present in 8% of mothers with UIC less than 100 microg/L. The median MIC was 93.5 microg /L. MIC was less than 50 microg /L in 19%. Grade 1 and 2 goiters were present in 11% and 8%, respectively, of women with MIC <50 mg/L. MIC and UIC levels were significantly correlated (r = 0.44, p < 0.0001). Iodine deficiency and goiter were associated (p < 0.0001). UIC and MIC concentrations are sufficient in Gorgan, Iran. However, individual infants remain at risk for low iodine intake via breast milk.

The NAS perchlorate review: questions remain about the perchlorate RfD

Human exposure to perchlorate is commonplace because it is a contaminant of drinking water, certain foods, and breast milk. The U.S. Environmental Protection Agency (EPA) conducted a perchlorate risk assessment in 2002 that yielded a reference dose (RfD) based on both the animal and human toxicology data. This assessment has been superceded by a recent National Academy of Science (NAS) review that derived a perchlorate RfD that is 20-fold greater (less stringent) than that derived by the U.S. EPA in 2002. The NAS-derived RfD was put on the U.S. EPA's Integrated Risk Information System (IRIS) database very quickly and with no further public review. In this commentary we raise concerns about the NAS approach to RfD development in three areas of toxicity assessment: the dose that the NAS described as a no observable adverse-effect level is actually associated with perchlorate-induced effects; consideration of uncertainties was insufficient; and the NAS considered the inhibition of iodine uptake to be a nonadverse effect. We conclude that risk assessors should carefully evaluate whether the IRIS RfD is the most appropriate value for assessing perchlorate risk.