The assessment of iodine status - populations, individuals and limitations

Thyroglobulin as a Sensitive Biomarker of Iodine Status in Mildly and Moderately Iodine-Deficient Pregnant Women

Pregnant women are more susceptible to iodine deficiency. However, there are limitations in existing indicators for the evaluation of iodine nutrition in pregnant women. The study aimed to explore whether thyroglobulin (Tg) can be used as a more sensitive biomarker for pregnant women with mild and moderate iodine deficiency. A repeated-measure study was conducted among 1332 pregnant women in Zhejiang Province, China. Serum and urine specimens were collected at a mean of 10, 17, and 32 weeks of pregnancy, respectively; thyroid-stimulating hormone (TSH), Tg, and urinary iodine concentrations were measured. Linear mixed effects models were used to determine the associations between interaction of iodine concentrations and increasing gestation week and TSH and Tg, where participants were divided by urinary iodine concentration (UIC). The median Tg concentration was 11.56, 11.45, and 12.43 μg/L in the first, second, and third trimesters, respectively. After controlling the covariates, the interaction effects between the iodine status and gestation week were significant for both TSH and Tg (p = 0.038 and p = 0.007, respectively). TSH increased with the week of gestation in both iodine concentration groups. Tg increased with advancing pregnancy in the iodine-deficient group whereas it did not in the iodine-sufficient group. There was no significant variation in TSH at each trimester, and Tg was higher in the iodine-deficient group than in the iodine-sufficient group. Tg may be a more sensitive iodine status biomarker than TSH for pregnant women with mild-to-moderate iodine insufficiency.

Agronomic Biofortification of Plants with Iodine and Selenium: A Potential Solution for Iodine and Selenium Deficiencies

Iodine and selenium deficiencies are widespread both in developed countries and developing countries. The soil is the fundamental source of iodine and selenium for plants, and iodine and/or selenium-depleted soil restrains the cultivation of crops to cover recommended daily intakes of iodine and selenium. Although food fortification strategies, including salt iodization, increase the dietary intake of these minerals, their global deficiencies have not been eliminated. Therefore, new strategies have been developed to prevent iodine and selenium deficiencies, and biofortification is one of them. The aim of this review is to assert the outcomes of the studies that investigate the optimum conditions for biofortification with iodine and selenium and to recognize the role of biofortification practices as a potential solution for preventing iodine and selenium deficiencies. The findings of studies show that biofortification with iodine and selenium can be a solution for iodine and selenium deficiencies. Agronomic biofortification is currently a more convenient method to increase selenium and iodine contents in plants. However, the most effective agronomic biofortification conditions are crucial to acquire biofortified food. Moreover, increasing the awareness of the producers and consumers on biofortification has a determinative role in the achievement of biofortification practices for human health. Although research about iodine and selenium biofortification has been increased, the effectiveness of biofortified foods to meet recommended daily intakes is still unknown. More research is needed to understand most effective biofortification conditions for plants and bioavailability of biofortified foods for humans.

Iodine Intake and its Interindividual Variability in Brazilian Pregnant Women: EMDI Brazil Study

Data on pregnant women's iodine intake are limited in Brazil. The aim of the study was to evaluate the contribution of foods, food groups, and food subgroups to the Brazilian pregnant women's iodine intake, and identify which food items explain the interindividual variability of their intake. A cross-sectional study with food consumption data of 2247 pregnant women from 24-h recalls was developed. Food items were classified according to the FAO/WHO GIFT classification, and their contribution to iodine intake and interindividual variability was assessed by the proportion of means method and linear regression, respectively. The mean usual iodine intake was 163.1 mcg (95% CI: 162.9-163.2). The food groups "spices and condiments," "cereals and their products," and "milk and milk products"; and the food subgroups "herbs and spices," "wheat and wheat-based products," "milk: fresh and processed," "dough-based sweets," and "eggs: fresh and processed" contributed to at least 80% of the iodine intake. Of these, only the food subgroups "milk," "dough-based sweets," and "eggs" did not explain the higher proportion (> 80%) of the interindividual variability. The contribution of "salt," "white French bread," "fluid whole milk," and "rice" to the iodine intake and its interindividual variability is highlighted. This study confirms the importance of "salt" as a dietary source of iodine and that few food groups and subgroups explained the difference in the iodine intake among pregnant women. Despite that, Brazilian staple foods, such as "rice," "beans," "eggs," "milk," and "bread" were identified as important for iodine intake and could be included in nutritional guidelines targeted to Brazilian pregnant women.

Prevalence of iodine deficiency and associated factors among school-age children in Ethiopia: a systematic review and meta-analysis

BACKGROUND

Currently, iodine deficiency has become a significant burden globally; where 2 billion people and 29.8% of school-age children are iodine deficient. It is a leading cause of preventable brain damage among children, resulting in impaired cognitive and motor development. Even though salt iodization was started to be implemented to alleviate this burden in Ethiopia, primary studies assessing iodine deficiency in the country show highly variable findings, and no systematic review was conducted to determine the pooled prevalence of the problem which makes it difficult to assess the effect of the intervention as well as to design appropriate and timely measures. Therefore, this systematic review and meta-analysis aimed to determine the pooled prevalence of iodine deficiency and the common factors affecting its occurrence among school-age children in Ethiopia.

METHOD

To obtain the eligible studies, databases (EMBASE, Scopus, Hinari, and PubMed), websites (Google and Google Scholar), and references of the eligible studies were searched systematically. Data were extracted using an Excel spreadsheet and analyzed using the STATA 17 version. The I2 test was used to assess heterogeneity between the studies. A DerSimonian and Laird random-effects model was used to estimate the pooled prevalence and pooled odds ratio. A funnel plot and Egger's test were used to detect publication bias.

RESULT

A total of 15 eligible studies, representing 15,611 school-age children, were included in the systematic review and meta-analysis. The pooled prevalence of iodine deficiency among school-age children in Ethiopia was found to be 58% (95%CI 44.00-77.00), while the highest prevalence was recorded in the Oromia Region, which was 64% (95% CI 49-79). Goitrogenic food consumption (adjusted odds ratio (AOR) 2.93, 95% CI 1.60-5.35) and being female (adjusted odds ratio (AOR) 1.87, 95% CI 1.43-2.44) showed a significant association with the prevalence of iodine deficiency.

CONCLUSION

Iodine deficiency among school-age children in Ethiopia was noticeably high. Goitrogenic food consumption and the sex of the child were determinant factors for the occurrence of iodine deficiency among the children. Therefore, appropriate advice should be given to households to limit goitrogenic foods in the diet of their children by giving due attention to their female children.

Maternal Thyroid Dysfunction During Pregnancy as an Etiologic Factor in Autism Spectrum Disorder: Challenges and Opportunities for Research

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with unknown etiology. Both genetic and environmental factors have been associated with ASD. Environmental exposures during the prenatal period may play an important role in ASD development. This narrative review critically examines the evidence for a relationship between maternal thyroid dysfunction during pregnancy and ASD in the child. Summary: Studies that assessed the associations of hypothyroidism, hyperthyroidism, hypothyroxinemia, thyroid hormone concentrations, or autoimmune thyroid disease with ASD outcomes were included. Most research focused on the relationship between hypothyroidism and ASD. Multiple population-based studies found that maternal hypothyroidism was associated with higher likelihood of an ASD diagnosis in offspring. Associations with other forms of maternal thyroid dysfunction were less consistent. Findings may have been affected by misclassification bias, survival bias, or publication bias. Studies using medical records may have misclassified subclinical thyroid dysfunction as euthyroidism. Two studies that assessed children at early ages may have misclassified those with ASD as typically developing. Most studies adjusted for maternal body mass index (BMI) and/or mental illness, but not interpregnancy interval or pesticide exposure, all factors associated with fetal survival and ASD. Most studies reported a combination of null and statistically significant findings, although publication bias is still possible. Conclusions: Overall, evidence supported a positive association between maternal thyroid dysfunction during pregnancy and ASD outcomes in the child, especially for hypothyroidism. Future studies could reduce misclassification bias by using laboratory measures instead of medical records to ascertain thyroid dysfunction and evaluating children for ASD at an age when it can be reliably detected. Survival bias could be further mitigated by adjusting models for more factors associated with fetal survival and ASD. Additional research is needed to comprehensively understand the roles of maternal levothyroxine treatment, iodine deficiency, or exposure to thyroid-disrupting compounds in the relationship between maternal thyroid dysfunction and child ASD outcomes.

Association study of urinary iodine concentrations and coronary artery disease among adults in the USA: National Health and Nutrition Examination Survey 2003-2018

Iodine is a vital trace element in the human body and is associated with several important coronary artery disease (CAD) risk factors. We aimed to explore the correlation between urinary iodine concentration (UIC) and CAD. Data from 15 793 US adults in the National Health and Nutrition Examination Survey (2003-2018) were analysed. We conducted multivariable logistic regression models and fitted smoothing curves to study the correlation between UIC and CAD. Furthermore, we performed subgroup analysis to investigate possible effect modifiers between them. We found a J-shaped association between UIC and CAD, with an inflection point at Lg UIC = 2·65 μg/l. This result indicated a neutral association (OR 0·89; 95 % CI 0·68, 1·16) between UIC and CAD as Lg UIC < 2·65 μg/l, but the per natural Lg [UIC] increment was OR 2·29; 95 % CI 1·53, 3·43 as Lg UIC ≥ 2·65 μg/l. An interaction between diabetes and UIC might exist. The increase in UIC results in an increase in CAD prevalence (OR 1·84, 95 % CI 1·32, 2·58) in diabetes but results in little to no difference in non-diabetes (OR 0·98, 95 % CI 0·77, 1·25). The J-shaped correlation between UIC and CAD and the interaction between diabetes and UIC should be confirmed in a prospective study with a series of UIC measurements. If excessive iodine precedes CAD, then this new finding could guide clinical practice and prevent iodine deficiency from being overcorrected.

Iodine deficiency and real-life supplementation ineffectiveness in Polish pregnant women and its impact on thyroid metabolism

Introduction

Iodine is a pivotal component of thyroid hormones, and its deficiency leads to negative pregnancy outcomes. Therefore, during gestation, additional iodine supplementation is recommended.

Objectives

By evaluating a group of women from western Poland, the study updated on iodine status during pregnancy and the effectiveness of iodine supplementation in relation to the maternal and neonatal thyroid function.

Patients and methods

A total of 91 women were recruited before the delivery between 2019 and 2021. During the medical interview, the patients declared their dietary supplements intake. Thyroid parameters (TSH, ft3, ft4, a-TPO, a-Tg, and TRAb) were measured in the serum of mothers and in the cord blood of newborns after birth. Urinary iodine concentration (UIC) and urine/creatinine (UIC/crea) ratio were assessed in single urine samples using a validated high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Neonatal TSH screening from dried blood spot was analyzed.

Results

Pregnant women showed a median (interquartile range) UIC of 106 (69-156) µg/liter and UIC/crea ratio of 104 (62-221) µg/g, whereas approximately 20% had UIC/crea below 50 µg/g, indicating iodine deficiency. The iodine supplementation ratio was 68%. No significant differences in UIC, UIC/crea and thyroid parameters were found between iodine supplemented and non-supplemented groups; however, the highest ioduria was detected when iodine was supplemented in addition to levothyroxine in comparison with both substances administered separately. Patients with UIC/crea within 150-249 µg/g demonstrated the lowest TSH and a-TPO levels. Screening TSH was above 5 mIU/liter in 6% of children.

Conclusions

Despite the national salt iodization and the recommendation to supplement iodine during gestation, the status of the abovementioned microelement and real-life intake revealed the ineffectiveness of the current iodine-deficiency prophylaxis model in pregnancy.

Association between urinary iodine concentration and the risk of papillary thyroid cancer by sex and age: a case-control study

Previous studies on dietary iodine intake and the risk of papillary thyroid cancer (PTC) have demonstrated inconsistent results. We aimed to evaluate the association between urinary iodine concentration (UIC), a surrogate biomarker for dietary iodine intake, and the risk of thyroid cancer stratified by sex and age in an iodine-sufficient area. A hospital-based case-control study was conducted in Seoul, South Korea. A total of 492 cases of newly diagnosed PTC and 595 controls were included. Compared with the lowest quartile of creatine-adjusted UIC (< 159.3 μg/gCr), the highest quartile (≥ 1037.3 μg/gCr) showed an increased risk of PTC (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.04-2.13), especially in those who were < 45 years old (p_trend = 0.01) compared with those who were ≥ 45 years old (p_trend = 0.48). For those who were < 45 years old, a positive association between creatinine-adjusted UIC and the risk of PTC was observed in both men (q4 vs. q1, OR 4.27, 95% CI 1.14-18.08) and women (OR 1.97, 95% CI 1.04-3.78). For those who were ≥ 45 years old, no association was found in any sex. Creatinine-adjusted UIC was positively associated with the risk of PTC, especially in those who were younger than 45 years for both men and women.

Sodium, Potassium and Iodine Intake in an Adult Population of Lithuania

Hypertension is a leading risk factor for cardiovascular events and death. A reduction in salt intake is among the most cost-effective strategies to reduce blood pressure and the risk of cardiovascular diseases. Increasing potassium lowers blood pressure and is associated with lower cardiovascular risk. Adequate iodine intake is important to prevent iodine deficiency disorders. Salt iodization is a key strategy to prevent such deficiency. In Lithuania, no surveys have been performed to directly assess sodium, potassium and iodine consumption. The aim of the present study was to measure sodium, potassium and iodine intake in a randomly selected adult Lithuanian adult population using 24 h urine collections, and to assess knowledge, attitudes and behavior towards salt consumption. Salt and potassium intakes were estimated in 888 randomly selected participants by 24 h urine sodium and potassium excretion and 679 individuals provided suitable 24 h urine samples for the analysis of iodine excretion. Average salt intake was 10.0 (SD 5.3) g/24 h and average potassium intake was 3.3 (SD 1.3) g/24 h. Only 12.5% of participants consumed less than 5 g/24 h of salt. The median value of urinary iodine concentration (UIC) was 95.5 μg/L. Our study showed that average salt intake is twice as high as the maximum level recommended by the World Health Organization while potassium and iodine intakes in Lithuania are below the recommended levels.

Vegan nutrition: a preliminary guide for health professionals

Since the beginning of the 21st century, interest in vegan diets has been rapidly increasing in most countries. Misconceptions about vegan diets are widespread among the general population and health professionals. Vegan diets can be health-promoting and may offer certain important advantages compared to typical Western (and other mainstream) eating patterns. However, adequate dietary sources/supplements of nutrients of focus specific to vegan diets should be identified and communicated. Without supplements/fortified foods, severe vitamin B12 deficiency may occur. Other potential nutrients of focus are calcium, vitamin D, iodine, omega-3 fatty acids, iron, zinc, selenium, vitamin A, and protein. Ensuring adequate nutrient status is particularly important during pregnancy, lactation, infancy, and childhood. Health professionals are often expected to be able to provide advice on the topic of vegan nutrition, but a precise and practical vegan nutrition guide for health professionals is lacking. Consequently, it is important and urgent to provide such a set of dietary recommendations. It is the aim of this article to provide vegan nutrition guidelines, based on current evidence, which can easily be communicated to vegan patients/clients, with the goal of ensuring adequate nutrient status in vegans.

Trends in Iodine Status Among U.S. Children and Adults: A Cross-Sectional Analysis of National Health and Nutrition Examination Survey Data from 2001-2004 to 2017-2020

Background: Iodine nutrition is an important public health issue. Trends in iodine status over time among U.S. schoolchildren and adults and factors mediating changes of iodine status were examined. Methods: In this cross-sectional study of National Health and Nutrition Examination Survey (NHANES) data, we estimated trends in the U.S. population using linear regression analyses. Representative samples of U.S. children and adults were enrolled in NHANES 2001-2020. The NHANES cycles were categorized into 5 four-year periods: 2001-2004, 2005-2008, 2009-2012, 2013-2016, and 2017-2020. The final sample sizes of children and adults for analysis were 4288 and 19,661, respectively. The estimated average requirement (EAR) (based on guidelines from the Institute of Medicine), was used to estimate the prevalence rate of inadequate iodine intake. Binary logistic regression analyses were used to investigate the association between iodine status and contributing factors. Results: From 2001-2004 to 2017-2020, among children, urinary iodine concentration (UIC) decreased from 243 to 166 μg/L (p_trend = 0.0057) and prevalence of iodine intake below the EAR rose from 15.4% to 27.6%. In adults, the UIC decreased from 153 to 116 μg/L (p_trend < 0.001) and prevalence of iodine intake below the EAR rose from 15.0% to 17.9%. A higher prevalence rate of iodine intake below the EAR was observed in females compared with males (children, 24.0% vs. 16.5%, p < 0.001; adults, 20.0% vs. 11.1%, p < 0.001). Inadequate iodine intake was less frequent among non-Hispanic White and Hispanic compared with non-Hispanic Black in children and adults. Adults without thyroid problems had a higher prevalence of inadequate iodine intake than those with thyroid problems (16.0% vs. 13.0%, p = 0.001). Inadequate iodine intake was less likely in the children who "sometimes" and "often" consumed milk products compared with children who "never or rarely" consumed milk products (OR = 0.60 [CI 0.30-1.21] and OR = 0.24 [CI 0.13-0.43], respectively). The prevalence of inadequate iodine intake among adults reporting "sometimes" (OR = 0.70 [CI 0.58-0.83]) and "often" consuming milk products was lower than those who "never or rarely" consumed them (OR = 0.36 [CI 0.30-0.44]). Conclusions: In this weighted survey, the prevalence of inadequate iodine intake increased from 2001-2004 to 2017-2020 among U.S. school-age children and adults. Sex, race, thyroid problems, and a decreased intake of milk products were significantly associated with iodine intake below the EAR.

A Meta-Analysis of the Effect of Iodine Excess on the Intellectual Development of Children in Areas with High Iodine Levels in their Drinking Water

The purpose of this meta-analysis is to comprehensively investigate the effect of iodine excess on children's intellectual development in areas with high iodine levels in their drinking water. We systematically searched the electronic databases and identified 17 publications (16 in Chinese and 1 in English) on the effect of iodine excess on children's intelligence published between January 31, 1985, and January 31, 2020. This meta-analysis included 14,794 children from 28 studies. The results showed that compared with the control group, the intelligence level of children in the high iodine group reduced significantly by 1.64 points (WMD=-1.64; 95% CI (-3.225, -0.049), Z=2.02, P<0.05). Subgroup analyses were performed according to the water iodine concentration, water iodine concentration of the control group, the intelligence test method, and regions of China (i.e., north and south). We noted that when the water iodine concentration was <300μg/L, 301-600μg/L, 600.1-900μg/L, and >900μg/L, the intelligence level of the high iodine groups decreased by varying degrees, although not statistically significant (all P>0.05). The water iodine concentration of the control group was divided into two groups (<150 μg/L and <100 μg/L) and the heterogeneity analysis showed that the heterogeneity of the control group decreased significantly when the concentration of water iodine was <150 μg/L, I² = 67.3%, P<0.001, which indicated a potential source of heterogeneity. The analyses by test method showed that among the studies which used the China Joint Raven's test, the intelligence level of children in the high iodine group was 0.86 points lower than in the control group (P>0.05). Conversely, we observed that among the studies which used the China Binet intelligence test and the binaphthalene intelligence test of Tanzhida in Japan to evaluate children's intelligence level, the intelligence level of children in the high iodine groups was significantly lower (3.65 points and 8.0 points, respectively) compared with the control groups (P<0.05). The analysis of the regions of China demonstrated that whereas the reduction in children's intelligence level from excess iodine in the north of China was not statistically significant (WMD=-0.16, 95% CI (-2.18, 1.85), P>0.05), the association was statistically significant in the southern part of China (WMD=-1.86, 95% CI (-3.57, -0.09), P<0.05). This study found that high iodine concentration was statistically significantly associated with a decline in intelligence level in children. Comparatively, the intelligence level of children who were exposed to high iodine concentrations reduced significantly by 1.64 points. These findings have public health implications.

Iodine: Its Role in Thyroid Hormone Biosynthesis and Beyond

The present review deals with the functional roles of iodine and its metabolism. The main biological function of iodine concerns its role in the biosynthesis of thyroid hormones (THs) by the thyroid gland. In addition, however, further biological roles of iodine have emerged. Precisely, due to its significant action as scavenger of reactive oxygen species (ROS), iodine is thought to represent one of the oldest antioxidants in living organisms. Moreover, iodine oxidation to hypoiodite (IO-) has been shown to possess strong bactericidal as well as antiviral and antifungal activity. Finally, and importantly, iodine has been demonstrated to exert antineoplastic effects in human cancer cell lines. Thus, iodine, through the action of different tissue-specific peroxidases, may serve different evolutionarily conserved physiological functions that, beyond TH biosynthesis, encompass antioxidant activity and defense against pathogens and cancer progression.

Association of Salt Iodization and Urine Iodine Concentration in Schoolchildren from Public Schools in Northeast of Brazil

Iodine deficiency (ID) is recognized as a leading risk factor for child development. Universal salt iodization (USI) is an effective and well-established intervention strategy for the prevention of iodine deficiency disorders (IDD). To evaluate the levels of iodine in household salt samples and the urinary iodine concentration (UIC) in schoolchildren aged 6 to 14 years in public schools in Bahia, Brazil. A cross-sectional study was conducted with 1231 students (6 to 14 years old) from 17 public schools in Bahia. The iodine concentration was evaluated in salt and UIC samples. The adapted Sandell-Kolthoff reaction was used to determine urinary iodine levels. A spectrophotometer (UV-Vis) was used to examine the reduction of ceric ammonium sulfate. A standard iodine solution using a potassium iodate was used to extrapolate the iodine concentrations. The total of 665 salt samples had a median iodine concentration of 24 mg/kg (25th-75th percentile 17.0 to 28.5 mg/kg). The largest proportion (79.6%) of salt samples had iodine concentration in the recommended range, 17.6% of the samples presented iodine at a salt concentration below the established level (<15 mg/kg) and a small proportion was above it (2.8%). The general mean urinary iodine concentration (MUIC) was 217.53 ± 28.30 μg/L and median was 205.50 μg/L. The students evaluated and the salt samples analyzed showed satisfactory results, as recommended by Brazilian legislation and nutritional recommendations of the World Health Organization (WHO).

Myoclonus From Intoxication by Bismuth Iodoform Paraffin Paste (BIPP) Nasopharyngeal Packing

Bismuth iodoform paraffin paste (BIPP) gauze is widely used as an antiseptic wound packing in otolaryngology, head, and neck surgery. Uncommonly, BIPP can cause intoxication. Our report highlights an elderly patient who developed encephalopathy and overt myoclonus after nasopharyngectomy secondary to intoxication by the components of the BIPP gauze. The patient’s impaired renal function, the amount of BIPP packing and the extensive nature of his wound likely predisposed him to BIPP toxicity. The myoclonus and delirium resolved promptly after removal of the BIPP packs. Clinicians should be aware of the clinical features of BIPP intoxication because of its common usage.

HPLC Analysis of the Urinary Iodine Concentration in Pregnant Women

Iodine is an essential component for fetal neurodevelopment and maternal thyroid function. Urine iodine is the most widely used indicator of iodine status. In this study, a novel validated ion-pair HPLC-UV method was developed to measure iodine concentration in clinical samples. A sodium thiosulfate solution was added to the urine sample to convert the total free iodine to iodide. Chromatographic separation was achieved in a Pursuit XRs C8 column. The mobile phase consisted of acetonitrile and a water phase containing 18-crown-6-ether, octylamine and sodium dihydrogen phosphate. Validation parameters, such as accuracy, precision, limits of detection and quantification, linearity and stability, were determined. Urinary samples from pregnant women were used to complete the validation and confirm the method's applicability. In the studied population of 93 pregnant women, the median UIC was lower in the group without iodine supplementation (117 µg/L, confidence interval (%CI): 95; 138) than in the supplement group (133 µg/L, %CI: 109; 157). In conclusion, the newly established ion-pair HPLC-UV method was adequately precise, accurate and fulfilled validation the criteria for analyzing compounds in biological fluids. The method is less complicated and expensive than other frequently used assays and permits the identification of the iodine-deficient subjects.

Evaluation of iodine nutritional status during pregnancy by estimated 24-h urinary iodine excretion: population variation range and individual accuracy

Objective:

To explore the accuracy of estimated 24-h urinary iodine excretion (24-h UIE_est) in assessing iodine nutritional status.

Design:

Fasting venous blood, 24-h and spot urine samples were collected during the day. The urinary iodine concentration (UIC) and urinary creatinine concentration (UCrC) were measured, and the urinary iodine-to-creatinine ratio (UI/Cr), 24-h UIE_est, and 24-h urinary iodine excretion (24-h UIE) were calculated. At the population level, correlation and consistency between UIC, UI/Cr, 24-h UIE_est and 24-h UIE were assessed using correlation analysis and Bland–Altman plots. At the individual level, receiver operating characteristic (ROC) curves were used to analyse the accuracy of the above indicators for evaluating insufficient and excessive iodine intake. The reference interval of 24-h UIE_est was established based on percentile values.

Setting:

Indicator can accurately evaluate individual iodine nutrition during pregnancy remains controversial.

Participants:

Pregnant women (n 788).

Results:

Using 24-h UIE as standard, the correlation coefficients of 24-h UIE_est from different periods of the day ranged from 0·409 to 0·531, and the relative average differences ranged from 4·4 % to 10·9 %. For diagnosis of insufficient iodine intake, the area under the ROC curve of 24-h UIE_est was 0·754, sensitivity and specificity were 79·6 % and 65·4 %, respectively. For diagnosis of excessive iodine intake, the area of 24-h UIE_est was 0·771, sensitivity and specificity were 66·7 % and 82·0 %, respectively. The reference interval of 24-h UIE_est was 58·43–597·65 μg.

Conclusions:

Twenty-four-hour UIE_est can better indicate iodine nutritional status at a relatively large sample size in a given population of pregnant women. It can be used for early screening at the individual level to obtain more lead time for pregnant women.

Reflection of Dietary Iodine in the 24 h Urinary Iodine Concentration, Serum Iodine and Thyroglobulin as Biomarkers of Iodine Status: A Pilot Study

BACKGROUND

The iodine status of the US population is considered adequate, but subpopulations remain at risk for iodine deficiency and a biomarker of individual iodine status has yet to be determined. The purpose of this study was to determine whether a 3 day titration diet, providing known quantities of iodized salt, is reflected in 24 h urinary iodine concentration (UIC), serum iodine, and thyroglobulin (Tg).

METHODS

A total of 10 participants (31.3 ± 4.0 years, 76.1 ± 6.3 kg) completed three, 3 day iodine titration diets (minimal iodine, US RDA, (United States Recommended Daily Allowance), and 3× RDA). The 24 h UIC, serum iodine, and Tg were measured following each diet. The 24 h UIC and an iodine-specific food frequency questionnaire (FFQ) were completed at baseline.

RESULTS

UIC increased an average of 19.3 μg/L for every gram of iodized salt consumed and was different from minimal to RDA (p = 0.001) and RDA to 3× RDA diets (p = 0.04). Serum iodine was different from RDA to 3× RDA (p = 0.006) whereas Tg was not responsive to diet. Baseline UIC was associated with iodine intake from milk (r = 0.688, p = 0.028) and fish/seafood (r = 0.646, p = 0.043).

CONCLUSION

These results suggest that 24 h UIC and serum iodine may be reflective of individual iodine status and may serve as biomarkers of iodine status.

24 h urinary creatinine excretion during pregnancy and its application in appropriate estimation of 24 h urinary iodine excretion

BACKGROUND

Urinary creatinine can be used to adjust urinary iodine to evaluate iodine nutritional status during pregnancy. However, the reference intervals and impact factors of urinary creatinine are unknown.

METHODS

24 h urine creatinine concentration (24 hUCr) and spot UCr at four different time periods of the day of pregnant women from Part 1 (n = 743) were measured. Linear regression analysis was performed to identify the impact factors of 24 h urinary creatinine excretion (24 hUCrE) and obtain the estimated 24 h urinary creatinine excretion (24 hUCrE_est). Then measured urinary iodine concentration (UIC) of 24 h and at fasting of pregnant women from Part 2 (n = 325), used spot urinary iodine to creatinine concentration ratio (UIC/UCr) and 24 hUCrE_est to calculate the estimated 24 h urinary iodine excretion (24 hUIE_est), finally checked the consistency and correlation of 24 hUIE_est and 24 h urinary iodine excretion (24 hUIE).

RESULTS

In Part 1, the median 24 hUCrE was 1.24(IQR0.98-1.76)g, and the reference interval was 0.61-2.93 g. The median 24 hUCr was 0.76 (IQR0.57-1.01)g/L, and the reference interval was 0.36-1.88 g/L. Multiple linear regression results showed that pregnancy weight was an influencing factor to 24 hUCrE after adjusting by gestational weeks, age, pre-pregnancy BMI, and percentage of body fat (F = 45.029, p＜0.001). In Part 2, there was no statistically significant difference between 24 hUIE_est and 24 hUIE (Z =-0.767, p = 0.443). Using 24hUIE as the gold standard, the relative average difference in 24hUIE_est was 4.2 %, the relative average differences for UIC and UIC/UCr were 32.4 % and 37.2 %. The reference interval of 24 hUIE and 24 hUIE_est were 88.43-585.90 μg and 50.97-700.39 μg, respectively.

CONCLUSIONS

The reference intervals of 24 hUCrE, spot UCr, 24 hUIE, and 24 hUIE_est during pregnancy were established. 24 hUCrE has important application value in iodine nutrition evaluation to gain more lead time for pregnant women with iodine nutrition-related diseases.

The association of lactating mothers' urinary and breast milk iodine levels with iodine nutrition status and thyroid hormone levels of newborns

Objective

To explore the iodine status of lactating mother-newborn pairs, and whether neonatal serum thyroid-stimulating hormone (TSH) can be used for estimation of iodine status of the population.

Materials and Methods

A total of 334 mothers and their healthy neonates were included. Urine, serum, and breast milk samples were obtained at 4th and 6th days of delivery. Urinary iodine concentration (UIC) was measured in urine samples of mothers and their neonates, as well as breast milk iodine concentration (BMIC) and serum thyroid hormone levels of neonates, were measured from the samples taken between the 4th and 6th days after birth.

Results

Median age of the mothers was 27 years (23-30). The median UIC of mothers and their newborns were 125 μg/L and 142 μg/L, respectively. The median BMIC was 138,0 μg/L. There was a significant positive correlation between the BMIC and UIC of neonates (r=0.276, p<0.001). The prevalence of neonatal serum TSH >10 mIU/L, which is suggestive of mild iodine deficiency (i.e. 3.0-19.9%), was 19.0%. However, there were no participants with iodine deficiency in lactating mothers and neonates according to UIC.

Conclusion

By previous reports, Aydın is iodine sufficient. Although 19% of the neonates had serum TSH levels >10 mU/L, which is suggestive of a mild iodine deficiency, iodine deficiency was observed in none of the neonates and their mothers. Therefore, it will be appropriate to investigate the role of neonatal TSH levels in a larger sample to assess the iodine status of the population.

Associations between maternal urinary iodine assessment, dietary iodine intakes and neurodevelopmental outcomes in the child: a systematic review

OBJECTIVE

Mild to moderate iodine deficiency during pregnancy has been associated with adverse neurodevelopmental outcomes in offspring. Few research studies to date combine assessment of urinary iodine (UIC and/or ICr), biomarkers that best reflect dietary intake, with reported dietary intake of iodine rich foods in their assessment of iodine deficiency. Thus, a systematic review was conducted to incorporate both these important measures.

DESIGN

Using PRISMA guidelines, a comprehensive search was conducted in three electronic databases (EMBASE®, MedLine® and Web of Science®) from January 1970-March 2021. Quality assessment was undertaken using the Newcastle Ottawa Scale. Eligible studies included reported assessment of iodine status through urinary iodine (UIC and/or ICr) and/or dietary intake measures in pregnancy alongside neurodevelopmental outcomes measured in the children. Data extracted included study author, design, sample size, country, gestational age, child age at testing, cognitive tests, urinary iodine assessment (UIC in μg/L and/or ICr in μg/g), dietary iodine intake assessment and results of associations for the assessed cognitive outcomes.

RESULTS

Twelve studies were included with nine reporting women as mild-moderately iodine deficient based on World Health Organization (WHO) cut-offs for urinary iodine measurements < 150 μg/l, as the median UIC value in pregnant women. Only four of the nine studies reported a negative association with child cognitive outcomes based on deficient urinary iodine measurements. Five studies reported urinary iodine measurements and dietary intakes with four of these studies reporting a negative association of lower urinary iodine measurements and dietary iodine intakes with adverse offspring neurodevelopment. Milk was identified as the main dietary source of iodine in these studies.

CONCLUSION

The majority of studies classified pregnant women to be mild-moderately iodine deficient based on urinary iodine assessment (UIC and/or ICr) and/or dietary intakes, with subsequent offspring neurodevelopment implications identified. Although a considerable number of studies did not report an adverse association with neurodevelopmental outcomes, these findings are still supportive of ensuring adequate dietary iodine intakes and urinary iodine monitoring throughout pregnancy due to the important role iodine plays within foetal neurodevelopment. This review suggests that dietary intake data may indicate a stronger association with cognitive outcomes than urinary iodine measurements alone. The strength of this review distinguishes results based on cognitive outcome per urinary iodine assessment strategy (UIC and/or ICr) with dietary data. Future work is needed respecting the usefulness of urinary iodine assessment (UIC and/or ICr) as an indicator of deficiency whilst also taking account of dietary intakes.

Intra-individual and inter-individual variations in iodine intake and excretion in adult women: implications for sampling

Iodine intake and excretion vary widely; however, these variations remain a large source of geometric uncertainty. The present study aims to analyse variations in iodine intake and excretion and provide implications for sampling in studies of individuals or populations. Twenty-four healthy women volunteers were recruited for a 12-d sampling period during the 4-week experiment. The duplicate-portion technique was used to measure iodine intake, while 24-h urine was collected to estimate iodine excretion. The mean intra-individual variations in iodine intake, 24-h UIE (24-h urinary iodine excretion) and 24-h UIC (24-h urinary iodine concentration) were 63, 48 and 55 %, respectively, while the inter-individual variations for these parameters were 14, 24 and 32 %, respectively. For 95 % confidence, approximately 500 diet samples or 24-h urine samples should be taken from an individual to estimate their iodine intake or iodine status at a precision range of ±5%. Obtaining a precision range of ±5% in a population would require twenty-five diet samples or 150 24-h urine samples. The intra-individual variations in iodine intake and excretion were higher than the inter-individual variations, which indicates the need for more samples in a study on individual participants.

Adequate Iodine Intake among Young Adults in Jiangsu Province, China Despite a Medium Iodine Knowledge Score

Lack of iodine knowledge might be a risk factor for inadequate iodine intake in populations. Therefore, we aimed to determine the relationship between iodine knowledge and intake in young Chinese adults. A cross-sectional study was conducted in Suzhou, China. Iodine intake was assessed using a validated 33-item iodine-specific Chinese food frequency questionnaire (FFQ) and iodine knowledge was determined using a Chinese iodine knowledge questionnaire. A total of 150 participants (mean age 20.3 years) completed the study. The median iodine intake plus iodized salt was 260 μg/d, indicating iodine sufficiency (>150 µg/d). The median iodine knowledge score was 16/24, suggesting a medium level of knowledge. The majority of participants correctly recognized fish and seafood (95%) and iodized salt (83%) as the most important dietary iodine sources. After adjusting for age and sex, studying in the science cluster and having received iodine education were the predictors of having a higher iodine knowledge score, with adjusted odd ratios (OR) of 4.33 (1.49, 12.61) and 2.73 (1.21, 6.14), respectively. In conclusion, young Chinese adults had an adequate iodine intake despite a medium iodine knowledge score. This study provides support that iodine fortification in China has been successful, but further research is required to more fully substantiate this finding.

Analytical evaluation of the new Seal Autoanalyzer 3 High Resolution for urinary iodine determination

Introduction

The aim of the study was to evaluate the analytical performance of the new colorimetric, automatic analyser, Seal AutoAnalyzer 3 High Resolution (Seal AA3 HR) (Seal Analytical, Wisconsin, USA) for urinary iodine measurement.

Materials and methods

This study included testing of several analytical features of the method involving: imprecision (within-run %CVr, between-run %CVb and total laboratory precision %CVl), measurement uncertainty, carryover, linearity and method comparison, with 70 urine samples including the measuring range (20 - 700 µg/L).

Results

Within-run, %CVb and %CVl of two control levels were 2.03% and 3.04%, 0.51% and 2.61%, and 2.09% and 4.01%, respectively. Carryover effect was less than 1%. The linearity was good in the range of urinary iodine values between 60 and 500 µg/L (R² = 0.99). Good agreement of urinary iodine values was found between manual technique and Seal AA3 HR, using Passing-Bablok regression (y = 7.84 (- 3.00 to 15.29) + 0.95 (0.90 to 1.00) x) and Blant-Altman test. Cusum test for linearity indicates that there is no significant deviation from linearity (P > 0.1).

Conclusions

The obtained results proved excellent precision, reproducibility and linearity, comparable to the already used, manual method. The New Seal AA3 HR automatic analyser is acceptable for urinary iodine measurement with very good analytical characteristics and can be used for urinary iodine epidemiological studies of the Croatian population.