Iodine Status of Infants and Toddlers under 2 Years of Age and Its Association with Feeding Behaviors and Maternal Iodine Status in Shanghai: A Quantile Regression Analysis.

It is crucial to provide adequate iodine nutrition to infants and toddlers for proper thyroid function and subsequent brain development. Infants are particularly vulnerable to iodine deficiency during the transition from a milk-based diet (breast milk and/or infant formula) to solid food. This study examines the current iodine levels of children during their first two years of life and investigates the association between these levels and feeding behaviors and the iodine status of their mothers in Shanghai, a city located in eastern China. A hospital-based cohort study was conducted to enroll mother-child pairs, where the child is aged 6-23 months, who visited community health service centers in the 16 districts of Shanghai, China. Data on socio-demographic factors and feeding behavior data were collected from the participants. The urinary iodine concentration (UIC) in both the young children and their mothers were analyzed. A total of 2282 mother-child pairs were included in this analysis. The median (p25-p75) UIC for lactating women, weaning women, and children were 121.3 µg/L (68.1-206.4 µg/L), 123.4 µg/L (58.4-227.2 µg/L), and 152.1 µg/L (75.8-268.3 µg/L), respectively. The UIC in children was found to be higher than that in their mothers (p < 0.001). Children who consumed less than 500 mL per day of formula milk in the last week had lower UICs compared with those who consumed 500 mL per day or more (p = 0.026). Furthermore, the children's UIC was positively correlated with the maternal UIC (rs = 0.285, p < 0.001). Multiple quantile regression analysis revealed a statistically significant positive association between maternal UIC and children's UIC between the 0.1 and 0.9 quantiles (all p < 0.001). We found that the iodine status of infants and toddlers, as well as of mothers, was sufficient. However, a large minority of children and mothers may be at risk of iodine deficiency. Furthermore, no associations between children's UIC and feeding behaviors were observed. Moreover, there was a positive correlation between the UIC of young children and their mothers.

Pregnant women at risk for iodine deficiency but adequate iodine intake in school-aged children of Zhejiang Province, China.

The median urinary iodine concentration (UIC) of school-aged children has been commonly used as a surrogate to assess iodine status of a population including pregnant women. However, pregnant women have higher iodine requirements than children due to increased production of thyroid hormones. The aim of the study was to evaluate the iodine status of pregnant women and children as well as their household salt iodine concentration (SIC) in Quzhou, Zhejiang Province, China. Eligible pregnant women and children from all six counties of Quzhou in 2021 were recruited into the study. They were asked to complete a socio-demographic questionnaire and provide both a spot urine and a household table salt sample for the determination of UIC and SIC. A total of 629 pregnant women (mean age and gestation weeks of 29.6 years and 21.6 weeks, respectively) and 1273 school-aged children (mean age of 9 years and 49.8% of them were females) were included in the study. The overall median UIC of pregnant women and children in our sample was 127 (82, 193) µg/L and 222 (147, 327) µg/L, respectively, indicating sufficient iodine status in children but a risk of mild-to-moderate iodine deficiency in pregnant women. Distribution of iodine nutrition in children varied significantly according to their sex and age (P < 0.05). The rate of adequately household iodised salt samples (18-33 mg/kg) provided by pregnant women and children was 92.4% and 90.6%, respectively. In conclusion, our results indicated a risk of insufficient iodine status in pregnant population of China, but iodine sufficiency in school-aged children. Our data also suggested that median UIC of children may not be used as a surrogate to assess iodine status in pregnant women.

Iodine Status and Its Influencing Factors in Hospitalized and Healthy Preschool-Age Children.

Iodine is a trace element necessary for synthesizing thyroid hormones. It is especially crucial for the neurodevelopment and intellectual development of children. Preschool-age children admitted to the hospital tend to have more fragile physical and mental health, but few studies demonstrate their iodine status. Our study aimed to investigate the iodine status of hospitalized and healthy preschool-age children and to explore the factors influencing them. From January to December 2021, 426 children aged 3-6 years were admitted to the respiratory department for pneumonia, bronchopneumonia, or bronchiectasis, but they could eat normally and were recruited as hospitalized children. Six hundred ten healthy children aged 3-6 years were included. We collected anthropometric measurements and urine samples from hospitalized and healthy preschool-age children, and iodine status was assessed through urinary iodine concentration (UIC) and urinary iodine/creatinine ratio (UI/Cr). UIC was 40.1 and 166.1 µg/L for hospitalized and healthy preschool-age children, respectively (P < 0.001). Urinary creatinine concentration (UCr) was 0.2 and 0.8 g/L for hospitalized and healthy preschool-age children, respectively (P < 0.001). UIC decreased with increasing height z-scores in hospitalized children (Spearman's rho = -0.11, P = 0.022). A significantly increased risk of UIC < 100 µg/L was found in hospitalized children (OR = 9.1 (6.8, 12.2), P < 0.001) when compared to healthy children. In conclusion, hospitalized preschool-age children are likelier to have iodine insufficiency than healthy preschool-age children, especially those with good linear growth. Measures should be implemented to ensure adequate iodine intake of preschool-age children during hospitalization to avoid affecting their intellectual and physical development. Due to lower UCr in hospitalized children, creatinine is not appropriate for assessing iodine status in hospitalized children.

Association Between Iodine Status and Prevalence of Hypothyroidism, Autoimmune Thyroiditis, and Thyroid Nodule: a Cross-Sectional Study in Shandong Province, China.

In this study, the aim was to investigate the correlation between varying levels of urinary iodine concentration (UIC) in adults and the occurrence of thyroid diseases, with the additional objective of determining the optimal iodine status level for adults. A cross-sectional study was conducted on adults from six areas with different drinking water iodine concentrations (WIC) without eating iodized salt in Heze and Jining counties, Shandong Province, China. A total of 1336 adults were included in this study, and drinking water samples, blood samples, urine samples, thyroid ultrasound, and a questionnaire were collected. UIC, free triiodothyronine (FT3), free thyroid hormone (FT4), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) were detected. There were no significant differences in the detection rates of hypothyroidism and thyroid autoimmunity (TAI) among the different median UIC groups (UIC < 100 µg/L, 100-199 µg/L, 200-299 µg/L, ≥ 300 µg/L). However, the detection rates of hypothyroidism were higher in the UIC < 100 µg/L group (16.67%) and the UIC ≥ 300 µg/L group (16.51%) compared to the other groups. The detection rate of TAI increased as UIC levels increased. The detection rate of thyroid nodule (TN) in the UIC < 100 µg/L group was significantly higher than that in the UIC 200-299 µg/L UIC group (χ2 = 10.814, P = 0.001). After adjusting confounding factors, it was found that low UIC (< 100 µg/L) was a risk factor for TN (OR 1.83, 95% CI [1.04-3.22]). Meanwhile, there no statistical difference between UIC 200 and 299 µg/L and UIC 100 and199 µg/L for OR of hypothyroidism, TAI, and TN. This study identified associations between different UIC levels and the prevalence of thyroid disorders, with low UIC (< 100 µg/L) posing a risk for TN, and the detection rate of TN and hypothyroidism was the lowest in UIC (200-299 µg/L) group. Therefore, the acceptable UIC range of 'adequate' iodine intake among adults can be widened from 100-199 µg/L to 100-299 µg/L.

Iodine status and determinants in adults in Norway - results from a population-based health examination survey (The HUNT Study).

Background: In Norway, there is a lack of knowledge about the iodine status in the general and older adult population, and there is no established national monitoring programme for iodine. Several studies have indicated that iodine deficiency is prevalent in subgroups of the population. Salt iodisation is currently being considered as a measure to increase the population iodine status. In this cross-sectional study, the aim was to evaluate iodine status and determinants in the adult and older adult population in Mid-Norway, before salt iodisation is likely to be initiated. Methods: The study sample was a subsample of participants in the fourth wave of the population-based Trøndelag Health Study (HUNT4, 2017-2019) with available spot-urine samples. This subsample included participants with 25-64 years (n = 500) and 70-79 years (n = 250). The urine samples were analysed for iodine and creatinine. Information on the habitual intake of milk/yoghurt, fish, supplement use, use of thyroid medication and relevant background factors was collected through a general questionnaire. Multivariable quantile regression was used to model differences in the median urinary iodine concentration (UIC) by determinants. Estimates were weighted to match the age and sex distribution of the Norwegian population aged 25-79 years in 2019. Results: Median UIC was 97 µg/L (95% confidence interval [CI]: 92, 103) indicating borderline iodine deficiency at a group level. The median UIC increased with age, and iodine status was insufficient in participants below age 55 years (median 92 µg/L [95% CI: 85, 99]). Important determinants of UIC were habitual milk/yoghurt intake, daily supplement use and current use of thyroid medication, but not intake of lean or fatty fish. Risk of mild-to-moderate iodine deficiency was seen in those with a low intake of milk/yoghurt, no supplement use and who did not use thyroid medication. No group was identified as being at risk of iodine excess. Conclusion: Iodine status was adequate in older adults but mildly deficient in adults under 55 years. Milk intake, supplement use and use of thyroid medication are important determinants of iodine intake in Norway.

Iodine Nutrition, Thyroid-stimulating Hormone, and Related Factors of Postpartum Women from three Different Areas in China: A Cross-sectional Survey.

Objective: Studies on the relationship between iodine, vitamin A (VA), and vitamin D (VD) and thyroid function are limited. This study aimed to analyze iodine and thyroid-stimulating hormone (TSH) status and their possible relationships with VA, VD, and other factors in postpartum women. Methods: A total of 1,311 mothers (896 lactating and 415 non-lactating) from Hebei, Zhejiang, and Guangxi provinces were included in this study. The urinary iodine concentration (UIC), TSH, VA, and VD were measured. Results: The median UIC of total and lactating participants were 142.00 µg/L and 139.95 µg/L, respectively. The median TSH, VA, and VD levels in all the participants were 1.89 mIU/L, 0.44 µg/mL, and 24.04 ng/mL, respectively. No differences in the UIC were found between lactating and non-lactating mothers. UIC and TSH levels were significantly different among the three provinces. The rural UIC was higher than the urban UIC. Obese mothers had a higher UIC and a higher prevalence of excessive TSH. Higher UICs and TSHs levels were observed in both the VD deficiency and insufficiency groups than in the VD-sufficient group. After adjustment, no linear correlation was observed between UIC and VA/VD. No interaction was found between vitamins A/D and UIC on TSH levels. Conclusion: The mothers in the present study had no iodine deficiency. Region, area type, BMI, and VD may be related to the iodine status or TSH levels.

Adequate iodine nutrition and higher salt intake in Chinese adults aged 18-59 years recommended by international organizations.

Iodine deficiency and excessive salt intake have adverse health effects. This study evaluated the iodine level and salt intake in Chinese adults aged 18-59 years after implementing the salt reduction program and compared with both the World Health Organization (WHO) and Chinese recommendations. Adults aged 18-59 years were randomly selected using multi-stage stratified random sampling in coastal urban area (CUA), non-coastal urban area (Non-CUA), coastal rural area (CRA), and non-coastal rural area (Non-CRA) of Fujian Province, China. Iodine, sodium, and creatinine concentrations in spot urine samples were measured. Knudsen equation was used to determine 24-h urinary iodine and sodium excretion. The median urinary iodine concentration (mUIC) and urinary sodium concentration (mUNaC) among adults (n = 3513) were 132.0 µg/L and 4.0 g/d, respectively. The mUIC and median daily iodine intake in CUA, Non-CUA, CRA and Non-CRA were 112.1, 127.5, 128.5, 167.5 µg/L and 189.6, 182.5, 199.4, 236.0 µg/d, respectively. The mUNaC and median daily salt intake (mDSI) in these four areas were 2.4, 2.8, 2.9, 2.9 g/L and 9.8, 10.4, 10.4, 10.6 g/d, respectively. The mUIC and DII of residents were higher in the Non-CRA than in the other three areas (P < 0.05). The UNaC and DSI of residents were lower in the CUA than in the other three areas (P < 0.05). The logistic regression demonstrated that the people living in CUA and Non-CUA consumed less salt compared with those in Non-CRA. Except for Non-CUA, the DII was lower (< 150 µg/d) among women of childbearing age in the low-salt intake group (< 5 g/d) compared with the high-salt intake group (≥ 5 g/d) (P < 0.05). Iodine nutrition in Chinese adults aged 18-59 years was sufficient, but the salt intake was substantially higher than the WHO and Chinese recommendations. Further policy implementation is needed to reduce salt intake and improve the monitoring of iodine levels in Chinese adults, especially in women of childbearing age.

Thyroid volume in Turkish school-age children living in an iodine-sufficient region.

OBJECTIVES: We aimed to obtain local normative data on thyroid volume evaluated by ultrasonography and iodine status by measuring urine iodine levels in school-age children living in Aydin province. METHODS: In this cross-sectional study, a sample comprising 1,553 cases was meticulously selected from a total cohort of 170,461 children aged 6-17, drawn from 21 distinct educational institutions located within the Aydin region, as participants in the investigation. Those with a known chronic disease or thyroid disease were excluded from the study. The children underwent physical examinations and ultrasonography imaging of the thyroid gland, and urine samples were collected to measure urinary iodine concentration (UIC). RESULTS: The median UIC was 189.5 (IQR=134.4) µg/L, which was optimal according to WHO criteria. Thyroid volume was found to be 4.6 (IQR=3.5) mL in girls and 4.2 (IQR=4.0) mL in boys (p=0.883). The thyroid volumes in our study were found to be smaller when compared to the WHO. According to WHO age and body surface area criteria, thyroid volume was over 97 % in 0.9 % (n=15) of cases. Thyroid volume was found to have a positive correlation with age, height, weight, body mass index (BMI), and body surface area (BSA) in both genders (p<0.001). However, there was no significant correlation between thyroid volume and UIC. CONCLUSIONS: This cross-sectional study provides normative data on thyroid volume and iodine status in school-age children in iodine-sufficient population, revealing a low prevalence of goiter and correlations between thyroid volume and anthropometric measures.

Iodine Intake Trends in United States Girls and Women between 2011 and 2020.

BACKGROUND: Usual intakes of iodine in United States girls and women, including pregnant and lactating women have not been adequately studied. Adequate intake of iodine is critical for neurodevelopment of girls, thyroid functions, and reproductive health of women. OBJECTIVES: This study aimed to examine the adequacy and trends of iodine intake of United States girls and women between 2011 and 2020. METHODS: We mapped the sources of United States girls and women's iodine intake from the 29 food groups between 2011 and 2020 using United States Department of Agriculture's iodine data release 2. The total food intakes from 2 d of dietary recall of the United States National Health and Nutritional Examination Survey and estimated iodine concentrations of the food groups were used to calculate the usual iodine intakes of female participants. Trends of usual intakes, urinary iodine concentrations (UIC), and estimated intake adequacy were calculated. RESULTS: Median usual intakes of iodine estimated from diet and supplements and UIC of United States girls and nonpregnant, nonlactating women declined between 2011 and 2020 in all 3 age groups: ≤14 y, 15-49 y old, and ≥50 y. Median usual intakes of iodine for pregnant and lactating United States women declined as well. Inadequacy levels of usual iodine intake were 9.9% for nonpregnant, nonlactating women of reproductive age 15-49 y old, 40.3% for lactating, and 10.2% for pregnant women in the 2017-2020 period. Intake insufficiencies estimated from UIC were 48.8%, 63.2%, and 31.3% for nonpregnant, nonlactating women of reproductive age 15-49 y old, pregnant and lactating women, respectively, in the 2017-2020 period. A significant decline in milk consumption might be one of the major contributors to the dietary iodine decline in United States women. CONCLUSIONS: Iodine intake of United States girls and women were on the decline between 2011 and 2020 and the increased inadequacy of iodine intake deserves public health attention.

Effect of previous administration of potassium iodine and different durations of low iodine diets for radioiodine therapy on the treatment of Graves' disease in iodine-rich areas.

PURPOSE: To examine whether adherence to a low-iodine diet (LID) enhances the therapeutic efficacy of radioiodine therapy (RAI) in Graves' hyperthyroidism (GH) in iodine-rich areas. METHODS: We retrospectively evaluated 185 patients with GH from Aichi (n = 114) and Hokkaido (n = 71) Prefectures. Patients aged ≥ 18 years with GH who underwent RAI between December 2012 and March 2022 were divided into subgroups based on pretreatment with anti-thyroid drug (ATD) or potassium iodide (KI). Patients were followed up with LID from 18 days (group A) or 7 days (group H) before RAI to 3 days after RAI. The dose of radioactive iodine 131 (131I) was adjusted to deliver > 100 Gy to the thyroid. The associations between urinary iodine concentration on UIC2 vs. 24hRU and UIC2 vs. the 1-year RAI success rate (SR) were investigated. RESULTS: Compared with UIC1, UIC2 was significantly decreased in all subgroups (P < 0.01). An inverse correlation between UIC2 and 24hRU was observed in the four groups; however, the difference was insignificant. The SR in groups A and H was 85% and 89%, respectively. Univariate analysis revealed no association between UIC2 and SR in each group. Additionally, stratification of the 185 patients into quartiles using UIC2 yielded no significant differences in SR (p = 0.79). CONCLUSIONS: LID sufficiently reduced UIC in patients undergoing RAI. Although a lower UIC2 may increase 24hRU, it did not increase the success of RAI. The benefit of LID in enhancing the efficacy of RAI in GH treatment remains uncertain.

Iodine Excess May Lead to Low Exam Score in Children Aged 8-10 Years.

Recent research has shown that iodine excess may damage children's intelligence. Years of monitoring results in Shanghai show the iodine status has approached the upper limit of the appropriate range for children aged 8-10 years, indicating a risk of iodine excess. We used multi-stage random sampling to select children. Sixteen districts of Shanghai were divided into five units based on geographic location, and one primary school was randomly selected from each unit. In each selected school, about 40 children aged 8-10 years were randomly recruited to measure their urinary iodine concentration (UIC), household salt iodine concentration (SIC), the score of the final unified exam of the last semester, and school canteen salt iodine concentration. The median UIC of 3213 children aged 8-10 years in Shanghai was 195.4 (122.0, 285.8) µg/L and exceeded 200 µg/L in 48.8% of the population. Household and school canteen iodized salt coverage rates were 60.3% and 82.5% respectively, and mean household and school canteen SICs were 21.51 ± 9.30 mg/kg and 25.29 ± 3.40 mg/kg respectively. By correcting for potential confounding factors, logistic regression demonstrated that compared to the adequate iodine status group, students in the slight iodine excess group were less likely to get "A" (score > 90) in math, Chinese, and English exams (Math: OR = 0.775, 95% CI = 0.660-0.911, P = 0.002; Chinese: OR = 0.707, 95% CI = 0.543-0.842, P < 0.001; English: OR = 0.720, 95% CI = 0.610-0.849, P < 0.001). In Shanghai, the iodine status of 8-10-year-old children is approaching the upper limit of the adequate range. Iodine excess in Shanghai may lead to low exam scores for students.

The use of breast milk iodine concentration in the first week of lactation as a biomarker of iodine status in breast-feeding women.

Breast milk iodine concentration (BMIC) is a promising indicator of iodine status in lactating women. However, there are limited data on its usefulness to reflect maternal iodine deficiency. Therefore, the aim of our study was to assess iodine concentration in breast milk and urine samples in exclusively breast-feeding women. Eligible pregnant women undergoing routine antenatal care in a large hospital in Shaanxi Province, China, were followed up from the third trimester of pregnancy until the first week of lactation. Urine samples (20 ml) were collected during pregnancy and lactation. Iodine concentration in samples was measured based on Sandell-Kolthoff reaction. Breast milk samples (5 ml) were provided during lactation. A receiver operating curve (ROC) was constructed to determine the diagnostic performance of BMIC. An iodine-specific FFQ was completed twice during pregnancy and lactation. A total of 200 women completed the study. The overall median BMIC was 89 µg/l, indicating iodine sufficiency (i.e. BMIC reference range between 60 and 465 µg/l). Women reported similar median urinary iodine concentration (UIC) during pregnancy and lactation (112 and 113 µg/l, respectively), but their iodine status differed - mild-to-moderate iodine deficiency during pregnancy and iodine sufficiency during lactation. The ROC for BMIC using UIC as a reference standard was 0·755 (95 % CI: 0·644, 0·866). In conclusion, this study demonstrated that women were iodine sufficient in the first week of lactation as assessed by UIC, which was consistent with BMIC. These findings suggested that BMIC is a useful biomarker to assess iodine status in lactating women.

Iodine status of school-aged children in the changing context of universal salt iodization program during 1997-2018 in Chongqing, China.

OBJECTIVE: To illustrate the changes of iodized salt usage, goiter rate of school-aged children and median urinary iodine concentration (MUIC) of school-aged children in Chongqing for the last 21 years. This study aims to estimate the variational provincial status of iodine nutrition and provide scientific evidence for fine-tuning and adaptation of the current program. METHODS: Different number of families and school children aged 8-10 years from Chongqing during 1997-2018 participated in the study. UIC and iodine content in table salt were measured. Thyroid volumes of students were examined and goiter prevalence was calculated across years. RESULTS: The median iodine content of table salt was negatively associated with years(r = -0.727, P < 0.01). The MUIC were decreased annually (ranged between 200 and 300 µg/L) and was negatively associated with year(r = -0.831, P < 0.01). Goiter of school-aged children in Chongqing was decreased from the highest rate of 23.58% in 1999 to 1.62% in 2018(Cochran-Armitage Trend Test: χ2=-30.695, P < 0.01). Thyroid volume were negatively associated with years(r = -0.962, P < 0.01) and had a positive relationship with MUIC 1997-2018 (r = 0.862, P < 0.01). CONCLUSIONS: The consumption of adequately iodized salt can eliminate Iodine deficiency disorders (IDD) in children, but possible excessive iodine intake from salt could result in high urinary iodine excretion and even goiter. A systematic, well-designed and continual program monitoring is essential to ensure the adequacy of iodine fortification levels and to regularly change the iodine concentration in household table salt.

Iodine intake in the Swiss population 100 years after the introduction of iodised salt: a cross-sectional national study in children and pregnant women.

PURPOSE: The Swiss voluntary salt iodisation programme has successfully prevented iodine deficiency for 100 years, but dietary habits are changing and today only one-third of processed foods contain iodised salt. We aimed to monitor the current iodine status in children and pregnant women. METHODS: We conducted a nationwide cross-sectional study in children (6-12 years) and pregnant women and measured the urinary iodine concentration (UIC) in spot urine samples. We estimated the iodine intake using UIC and urinary creatinine concentration (UCC) and determined the prevalence of intakes below the average requirement (AR) using the SPADE method. We measured dried blood spot (DBS) thyroglobulin (Tg), TSH and total T4 in pregnant women. RESULTS: The median UIC was 127 µg/L (bootstrapped 95% CI 119, 140, n = 362) in children and 97 µg/L (bootstrapped 95% CI 90, 106, n = 473) in pregnant women. The estimated prevalence of inadequate iodine intake (< 65 µg/day) was 5.4% (bootstrapped 95% CI 0.0, 14.6) in children. Half (47%) of the women consumed iodine-containing multivitamin and mineral supplements (≥ 150 µg/day). Compared to non-users, users had higher median UIC (129 vs. 81 µg/L, P < 0.001), lower prevalence of inadequacy (< 160 µg/day; 0.2 vs. 31%) and lower DBS-Tg (23 vs. 29 µg/L, P < 0.001). All women were euthyroid. CONCLUSIONS: The Swiss diet and current salt fortification provides adequate iodine intake in children, but not in all pregnant women. Iodine supplements cover the dietary gap in pregnancy but are not universally consumed. Therefore, improved use of iodised salt in processed foods is desired to ensure adequate iodine intake in all population groups. This trial was registered at clinicaltrials.gov as NCT04524013.

Comparison of Thyroglobulin and Thyroid Function in Pregnant Women between Counties with a Median Urinary Iodine Concentration of 100-149 µg/L and 150-249 µg/L.

Objective: This study explored whether thyroglobulin and thyroid disease prevalence rates were higher in pregnant Chinese women with a median urinary iodine concentration of 100-149 µg/L, compared with those with a median urinary iodine concentration of 150-249 µg/L maintained through sustainable universal salt iodization. Methods: This was a cross-sectional study in which 812 healthy pregnant women were enrolled to collect samples of their household edible salt, urine, and blood during their routine antenatal care in the 18 counties in Fujian Province, China. The levels of salt iodine concentration, urinary iodine concentration (UIC), free triiodothyronine (FT3), free thyroid hormone (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), thyroid peroxidase antibody and thyroglobulin antibody were assessed during the routine antenatal care visits. Results: The median UIC (mUIC) in pregnant women was 130.8 µg/L (interquartile range = 91.5-198.1 µg/L) in the counties with an mUIC of 100-149 µg/L (Group I), and 172.0 µg/L (interquartile range = 123.5-244.4 µg/L) in the counties with an mUIC of 150-249 µg/L (Group II). Goiter prevalence and thyroid nodule detection rates showed no difference between Group I and Group II ( P > 0.05). Except for FT4 values, the TSH, FT4, FT3, Tg and Tg values > 40 (µg/L) and the thyroid diseases prevalence rate (TDR) showed no significant differences between Group I and Group II ( P > 0.05), whether or not iodine supplementation measures were taken. Conclusion: Compared with an mUIC of 150-249 µg/L, not only there was no difference in thyroid morphology, but also the Tg value, rate of Tg values > 40 µg/L, and TDR were not higher in pregnant women in the counties with an mUIC of 100-149 µg/L achieved through sustainable universal salt iodization in Fujian Province, China.

Do Postpartum Maternal Iodine Status or Supplementation Affect Thyroid Function After Delivery? A Systematic Review and Meta-Analysis.

The aim of this systematic review and meta-analysis was, for the first time, to explore whether postpartum maternal iodine status or supplementation is associated with thyroid function after delivery. The MEDLINE/PubMed, Web of Science, Embase, and Scopus were searched up to December 2021 to identify relevant studies. The pooled mean thyroid stimulating hormone (TSH), free thyroxine (fT4), and thyroxine (T4) concentrations and 95% confidence intervals (CIs) were estimated based on maternal urinary iodine concentration (UIC) (< 50, 50-100, 100-200, and > 200 µg/L) or breast milk iodine concentration (BMIC) (< 100 µg/L vs. ≥ 100 µg/L) during postpartum. A fixed/random effects model was used based on the absence/presence of heterogeneity, respectively. The study is registered with PROSPERO, number CRD42022336145. A total of 2175 studies were identified, of which 18 were eligible for the meta-analysis. The pooled values for TSH, fT4, and T4 concentrations in all subgroups were within the normal range; however, except for TSH, comparing the 95% CI showed no statistically significant difference among different subgroups. The pooled mean for TSH concentration in women with UIC > 200 µg/L was 2.23 mIU/L, whereas the corresponding values in women with UIC < 50, 50-100 and 100-200 µg/L were 0.56, 0.56 and 0.95 mIU/L, respectively. Thyroid hormones in women with BMIC < 100 µg/L and ≥ 100 µg/L were within the normal range. Iodine supplementation during postpartum was not associated with any differences in thyroid parameters, compared to non-supplemented women. In conclusion, iodine status or supplementation had no effect on thyroid hormones in postpartum women.

Iodine status and associated dietary factors among preschool children in Shanghai.

Children aged 3-6 years undergo a critical stage of growth and development and are irreversibly affected by their iodine status. In order to reveal iodine status in preschool children, we detected iodine concentrations in urine samples from 1382 children aged 3-6 years based on a cross-sectional study. The median urinary iodine concentration (UIC) of children was 193.36 µg/L and was 336.96 µg/g·Cr corrected for creatinine. The study developed a link between dietary habits and iodine status, revealing that regular calcium supplement (OR: 1.79, (95% CI: 1.03, 3.12)) increased deficiency risk, while moderate seafood consumption (OR: 0.60, (95% CI: 0.38, 0.95)) decreased it. Additionally, modest intake of shellfish (OR: 0.58, (95% CI: 0.33, 1.00)), vegetables (OR: 0.61, (95% CI: 0.38, 0.97)), and eggs (OR: 0.53, (95% CI: 0.30, 0.95)) was found to protect against excess iodine. The findings underline the importance of balanced diets and various nutrients' roles in preschoolers' iodine status.

Iodine Concentration in the Breast Milk and Urine as Biomarkers of Iodine Nutritional Status of Lactating Women and Breastfed Infants in Taiwan.

Breast milk iodine concentration (BMIC) can be different when median urinary iodine concentration (UIC) is similar. The BMIC, UIC/creatinine (Cr), estimated 24-h urinary iodine excretion (24-h UIE) of lactating women in Taiwan is unknown. This study enrolled lactating women from Taipei Veterans General Hospital (August 2021-February 2023). Each participant provided a random spot urine sample, two breast milk samples, a blood sample, and completed a food frequency questionnaire on the same day. Iodine measurement was performed by inductively coupled plasma mass spectrometry. The median UIC of the enrolled 71 women was 91.1 µg/L, indicating insufficient iodine status; however, the median BMIC was 166.6 µg/L and this suggested that the amount of iodine delivered through breast milk was adequate for the breastfed infants. BMIC was correlated with UIC/Cr and 24-h UIE (both rs = 0.49) but not with UIC (rs = 0.18) or thyroid stimulating hormone (rs = 0.07). Women who did not consume dairy products (adjusted odds ratio: 24.41, 95% confidence interval: 1.26-471.2) and multivitamins (adjusted odds ratio: 8.26, 95% confidence interval: 1.76-38.79) were at increased odds for having lower BMIC. The results suggest that measuring maternal UIC alone may not be sufficient, as BMIC, UIC/Cr, and 24-h UIE are all important biomarkers. Ingestion of dairy products and multivitamins were independently associated with BMIC.

Association between iodine nutrition and cervical lymph node metastasis of papillary thyroid microcarcinoma.

We aimed to investigate the association between iodine intake and nodal metastasis stratified by central lymph node metastasis (CLNM) and lateral lymph node metastasis (LLNM) of papillary thyroid microcarcinoma (PTMC). Urinary iodine concentration (UIC) and clinicopathological characteristics were used to identify factors associated with CLNM and LLNM using logistic regression analysis. A sum of 3,858 PTMC patients were enrolled. The median UIC (MUI) of patients with CLNM or LLNM was not statistically different from those without nodal metastasis. Male patients had a higher MUI than females (183.4 µg/L vs. 173.6 µg/L). Female patients with extracapsular extension had a higher MUI than those without it (210.0 µg/L vs. 172.1 µg/L). Male patients with LLNM had a significantly lower MUI than those without LLNM (134.7 µg/L vs. 187.9 µg/L). Female patients with more than adequate iodine intake were more likely to present with CLNM and extrathyroidal extension than those with adequate iodine intake with an odds ratio (95% confidence interval) of 1.23 (1.01-1.51) and 1.59 (1.09-2.32) after adjustment. Iodine nutrition was not found to be associated with LLNM. In addition, patients with a younger age, larger tumors, extrathyroidal extension, and intrathyroidal spread were more likely to be CLNM, whereas nodular goiter presented with a protective factor; CLNM was the only factor associated with LLNM of PTMC in both genders. In conclusion, iodine nutrition has a much closer association with female than male patients, and high iodine intake may be associated with CLNM and extrathyroidal extension in female PTMC patients.