Consequences of iodine deficiency and excess in pregnant women: an overview of current knowns and unknowns

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 Metabolism in Urine and Breast Milk among Lactating Women with Adequate Iodine

BACKGROUND

In lactating women, iodine metabolism is regulated and maintained by the kidneys and mammary glands. Limited research exists on how iodine absorbed by lactating women is distributed between the kidneys and breasts.

OBJECTIVES

This study aimed to accurately evaluate the total iodine intake (TII), urinary iodine excretion (UIE), and breast milk iodine excretion (BMIE) in lactating women and explore the relationship between TII and total iodine excretion (TIE).

METHODS

A 7-d iodine metabolism study was conducted on 41 lactating women with a mean age of 30 y in Yuncheng and Gaoqing, China, from December 2021 to August 2023. TII and TIE were calculated by measuring the iodine content in food, water, 24-h urine, feces, and breast milk. The urinary iodine excretion rate (UIER), breast milk iodine excretion rate (BMIER), and partitioning of iodine excretion between urine and breast milk were determined.

RESULTS

Iodine metabolism studies were performed for 285 d. The median TII and TIE values were 255 and 263 μg/d, respectively. With an increase in TII, UIER, and BMIER, the UIE and BMIE to TII ratio exhibited a downward trend. The median UIER, BMIER, and proportion of iodine excreted in urine and breast milk were 51.5%, 38.5%, 52%, and 37%, respectively. When the TII was <120 μg/d, the BMIER decreased with the increase of the TII (β: -0.90; 95% confidence interval: -1.08, -0.72).

CONCLUSIONS

When maternal iodine intake is low, the proportion in breast milk increases, ensuring sufficient iodine nutrition for infants. In addition, the UIE of lactating women with adequate iodine concentrations is higher than their BMIE. This study was registered at clinicaltrials.gov as NCT04492657.

Association between maternal and cord blood thyroid hormones, and urine iodine concentration with fetal growth

OBJECTIVES

We planned to evaluate the association of fetal and maternal thyroid hormones and maternal iodine status with neonates' anthropometric parameters.

METHODS

In this cross-sectional study, levels of thyrotropin were measured in maternal serum in the first trimester of pregnancy, and thyrotropin (TSH) and free thyroxin (fT4) were measured in cord blood serum samples at birth. Urinary iodine concentration (UIC) levels in random urine samples of mothers were measured in the third trimester of pregnancy. The relationship between UIC and thyroid hormone levels of mothers with neonates' anthropometric birth parameters of neonates was evaluated.

RESULTS

One hundred eighty-eight mother-newborn pairs completed the study. Mean (SD) of cord blood TSH (CB-TSH), cord blood-free thyroxin (CB-FT4) values, and maternal TSH (M-TSH) levels were 8.8 (7.3) mIU/L, 1.01 (0.2) ng/dL, and 2.2 (0.9) mIU/L, respectively. After adjusting for confounders, there was a positive significant association between female neonate length and maternal TSH and log log-transformed CB TSH (LN_CB-TSH) (p<0.05). Median UIC (Q1-Q3) was 157 (53-241) μg/L, and there was no association between birth weight, birth length, and head circumferences of neonates and mothers' UIC (p>0.05).

CONCLUSIONS

We found a positive correlation between maternal TSH in the first trimester of pregnancy and the birth length of newborns, and a negative correlation was observed between CB-TSH and birth length in girls, but it did not provide conclusive evidence for the relationship between maternal and neonatal thyroid hormone levels and birth weight. There was no association between maternal UIC levels in the third trimester and birth anthropometric parameters.

Prenatal Iodine Intake and Maternal Pregnancy and Postpartum Depressive and Anhedonia Symptoms: Findings from a Multiethnic US Cohort

Objective: Emerging evidence suggests that essential trace elements, including iodine, play a vital role in depressive disorders. This study investigated whether prenatal dietary iodine intake alone and in combination with supplemental iodine intake during pregnancy were associated with antepartum and postpartum depressive and anhedonia symptoms. Methods: The study population included 837 mothers in the PRogramming of Intergenerational Stress Mechanisms (PRISM) study. The modified BLOCK food frequency questionnaire was used to estimate prenatal dietary and supplemental iodine intake, while the 10-item Edinburg Postpartum Depression Scale (EPDS) ascertained depressive symptoms. Analyses considered the global EPDS score and the anhedonia and depressive symptom subscale scores using dichotomized cutoffs. Logistic regression estimating odds ratios and 95% confidence intervals (CIs) assessed associations of iodine intake in the second trimester of pregnancy and 6-month postpartum depressive and anhedonia symptoms considering dietary intake alone and combined dietary and supplementary intake in separate models. Results: Most women were Black/Hispanic Black (43%) and non-Black Hispanics (35%), with 39% reporting a high school education or less. The median (interquartile range, IQR) dietary and supplemental iodine intake among Black/Hispanic Black (198 (115, 337) µg/day) and non-Black Hispanic women (195 (126, 323) µg/day) was higher than the overall median intake level of 187 (116, 315) µg/day. Relative to the Institute of Medicine recommended iodine intake level of 160-220 µg/day, women with intake levels < 100 µg/day, 100-<160 µg/day, >220-<400 µg/day and ≥400 µg/day had increased adjusted odds of 6-month postpartum anhedonia symptoms (aOR = 1.74 (95% CI: 1.08, 2.79), 1.25 (95% CI: 0.80, 1.99), 1.31 (95% CI: 0.82, 2.10), and 1.47 (95% CI: 0.86, 2.51), respectively). The corresponding estimates for postpartum global depressive symptoms were similar but of smaller magnitude. Conclusions: Prenatal iodine intake, whether below or above the recommended levels for pregnant women, was most strongly associated with greater anhedonia symptoms, particularly in the 6-month postpartum period. Further studies are warranted to corroborate these findings, as dietary and supplemental iodine intake are amenable to intervention.

Assessment of iodine nutritional status and gestational thyroid function reference ranges during the first trimester of pregnancy in Taiwan

BACKGROUND

Iodine nutrition is critical for fetal neurodevelopment in the first trimester of pregnancy, a period associated with dramatic changes in thyroid function. The aim of this study was to evaluate iodine nutritional status and thyroid function reference ranges in the first trimester in Taiwan.

METHODS

Pregnant women aged 20 years and above in the first trimester were recruited in Taipei Veterans General Hospital, Taiwan from March 2019 to July 2022. Each participant provided a spot urine sample for measurement of urinary iodine concentration (UIC) and a blood sample for checkup of thyroid function and thyroid autoantibodies. A simple food frequency questionnaire was also completed.

RESULTS

A total of 209 women with a mean age of 32.9 ± 4.4 years were enrolled. The median UIC was 160.9 μg/L (interquartile range [IQR]: 105.0-246.2 μg/L), indicating overall iodine sufficiency. The gestational thyroid function reference ranges were: thyroid stimulating hormone (TSH) (median: 0.93 [0.007-2.9] µIU/mL), free T4 (1.3 [0.93-2.2] ng/dL), free T3 (3.0 [2.3-5.0] ng/dL), total T4 (9.9 [6.4-16.9] ng/dL), and total T3 (135 [88-231] ng/dL). If the nonpregnant reference range of serum TSH was used, eight women (4.8%) would be misclassified as having subclinical hyperthyroidism, and two women (1.2%) with subclinical hypothyroidism would be missed. In multivariate analysis, nulliparous (adjusted odds ratio [OR] from model 1-3: 2.02, 2.05, 2.02; 95% CI, 1.08-3.77, 1.10-3.81, 1.11-3.66; p = 0.027, 0.023, 0.022, respectively) and multivitamin nonusers (adjusted OR from model 1-3: 1.86, 1.85, 1.78; 95% CI, 1.04-3.34, 1.03-3.32, 1.004-3.71; p = 0.038, 0.039, 0.049, respectively) had increased odds of having lower UIC levels <150 μg/L.

CONCLUSION

The iodine nutritional status in the first trimester is adequate in Taiwan; however, certain subgroups such as nulliparous and multivitamin nonusers are still at risk for iodine deficiency. Gestational thyroid function reference ranges are needed for correct diagnosis of thyroid dysfunction in pregnancy.

Salivary iodine concentration in pregnant women and its association with iodine status and thyroid function

PURPOSE

There have been no reports on the application of salivary iodine concentration (SIC) in evaluating iodine nutrition in pregnant women. This study aimed to clarify the relationship between SIC and indicators of iodine nutritional status and thyroid function during pregnancy, to investigate whether salivary iodine can be applied to the evaluation of iodine nutritional status in pregnant women, and to provide a reference basis for establishing a normal range of salivary iodine values during pregnancy.

METHODS

Pregnant women were enrolled in the Department of Obstetrics, the people's hospital of Yuncheng Country, Shandong Province, from July 2021 to December 2022, using random cluster sampling. Saliva, urine, and blood samples were collected from pregnant women to assess iodine nutritional status, and venous blood was collected to determine thyroid function.

RESULTS

A total of 609 pregnant women were included in this study. The median spot urinary iodine concentration (SUIC) was 261 μg/L. The median SIC was 297 μg/L. SIC was positively correlated with SUIC (r = 0.46, P < 0.0001), 24-h UIC (r = 0.30, P < 0.0001), 24-h urinary iodine excretion (24-h UIE) (r = 0.41, P < 0.0001), and estimated iodine intake (EII) (r = 0.52, P < 0.0001). After adjusting for confounders, there was a weak correlation between SIC and serum total iodine and serum non-protein-bound iodine (P = 0.02, P = 0.04, respectively). Pregnant women with a SIC < 176 μg/L had a higher risk of insufficient iodine status (OR = 2.07, 95% CI 1.35-3.19) and thyroid dysfunction (OR = 2.71, 95% CI 1.18-6.21) compared to those with higher SIC. Those having SIC > 529 μg/L were more likely to have excessive iodine status (OR = 2.82, 95% CI 1.81-4.38) and thyroid dysfunction (OR = 3.04, 95% CI 1.36-6.78) than those with lower SIC values.

CONCLUSION

SIC is associated with urinary iodine concentration and thyroid function in pregnant women. SIC < 176 μg/L was associated with an increased risk for iodine deficiency and hypothyroxinemia, while SIC > 529 μg/L was related to excess and thyrotoxicosis. SIC can be used as a reference indicator for evaluating the iodine nutrition status of pregnant women, but it needs further investigation and verification.

TRIAL REGISTRATION

NCT04492657(Aug 9, 2022).

Study of iodine transport and thyroid hormone levels in the human placenta under different iodine nutritional status

Iodine and thyroid hormones (TH) transport in the placenta are essential for fetal growth and development, but there is little research focus on the human placenta. The research aimed to investigate iodine and TH transport mechanisms in the human placenta. The placenta was collected from sixty healthy pregnant women. Urinary iodine concentration (UIC), serum iodine concentration (SIC), placenta iodine storage (PIS) and the concentration of serum and placenta TH were examined. Five pregnant women were selected as insufficient intake (II), adequate intake (AI) and above requirements intake (ARI) groups. Localisation/expression of placental sodium/iodide symporter (NIS) and Pendrin were also studied. Results showed that PIS positively correlated with the UIC (R = 0·58, P < 0·001) and SIC (R = 0·55, P < 0·001), and PIS was higher in the ARI group than that in the AI group (P = 0·017). NIS in the ARI group was higher than that in the AI group on the maternal side of the placenta (P < 0·05). NIS in the II group was higher than that in the AI group on the fetal side (P < 0·05). In the II group, NIS on the fetal side was higher than on the maternal side (P < 0·05). Pendrin was higher in the II group than in the AI group on the maternal side (P < 0·05). Free triiodothyronine (r = 0·44, P = 0·0067) and thyroid-stimulating hormone (r = 0·75, P < 0·001) between maternal and fetal side is positively correlated. This study suggests that maternal iodine intake changes the expression of NIS and Pendrin, thereby affecting PIS. Serum TH levels were not correlated with placental TH levels.

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.

Impact of Maternal Environment and Inflammation on Fetal Neurodevelopment

During intrauterine life, external stimuli including maternal nutrition, lifestyle, socioeconomic conditions, anxiety, stress, and air pollution can significantly impact fetal development. The human brain structures begin to form in the early weeks of gestation and continue to grow and mature throughout pregnancy. This review aims to assess, based on the latest research, the impact of environmental factors on fetal and neonatal brain development, showing that oxidative stress and inflammation are implied as a common factor for most of the stressors. Environmental insults can induce a maternal inflammatory state and modify nutrient supply to the fetus, possibly through epigenetic mechanisms, leading to significant consequences for brain morphogenesis and neurological outcomes. These risk factors are often synergic and mutually reinforcing. Fetal growth restriction and preterm birth represent paradigms of intrauterine reduced nutrient supply and inflammation, respectively. These mechanisms can lead to an increase in free radicals and, consequently, oxidative stress, with well-known adverse effects on the offspring's neurodevelopment. Therefore, a healthy intrauterine environment is a critical factor in supporting normal fetal brain development. Hence, healthcare professionals and clinicians should implement effective interventions to prevent and reduce modifiable risk factors associated with an increased inflammatory state and decreased nutrient supply during pregnancy.

Clinical considerations of emergent oral manifestations during pregnancy

Pregnancy is a special period for developing and treating oral diseases. Oral emergencies during pregnancy need to be handled appropriately. Changes in the physiological environments and personal habits of pregnant women increase susceptibility to some oral diseases. However, clinical treatment strategies are limited due to the need to ensure the safety of pregnant women and fetuses. Pregnant women should obtain oral health knowledge and enhance their awareness. Dentists should adhere to the principle of "prevention before pregnancy, controlling symptoms during pregnancy, and treating diseases after pregnancy" for different pregnancy periods. They should also formulate appropriate treatment plans to control emergencies, prevent disease progression, and avoid harmful effects on pregnant women by using the safest, simplest, and most effective strategies that avoid adverse effects on fetuses. Pregnant women and dentists should combine prevention and treatment while collaborating in maintaining oral health during pregnancy. This article focuses on the principles of treatment during pregnancy, and the treatment timing, clinical management, and treatment strategies of different diseases causing oral emergencies during pregnancy are reviewed.

Determination of the Elemental Iodine in Human Breast Milk by Inductively Coupled Plasma mass Spectrometry

Adequate iodine status in lactating women is defined by a maternal median urinary iodine concentration (UIC) ≧ 100 µg/L. However, the above-mentioned criterion does not account for the secretion of iodine into breast milk and could not truly reflect the amount of iodine delivered to the infants. Measuring breast milk median iodine concentration (BMIC) is crucial, but the method to measure BMIC has not been developed and validated in Taiwan. We adopted the ammonia dilution method without prior sample digestion to measure BMIC by inductively coupled plasma mass spectrometry (ICP-MS). Samples and iodate calibrators were prepared into an aqueous solution containing Triton X-100, 0.5% ammonia solution, and tellurium (128Te) as the internal standard. Precision, accuracy, serial dilution, and recovery tests were performed for method validation. The range of intra-assay and inter-assay coefficient of variation for the four human breast milk samples with different iodine concentrations were 3.2-4.7% and 2.3-5.5%, respectively. The standard NIST 1549 milk powder was prepared into three different concentrations of 50 µg/L, 100 µg/L, and 200 µg/L to assess the accuracy; the bias was < 5%. A recovery of 95-105% was achieved for four human breast milk samples spiked with sodium iodide solution. The serial dilution test confirmed linearity up to 0.998. The limit for detection and quantification was 0.78 µg/L and 2.34 µg/L, respectively. The results of the current study confirmed that this ICP-MS method is accurate and reliable in measuring BMIC.

Chronic Excess Iodine Intake Inhibits Bone Reconstruction Leading to Osteoporosis in Rats

BACKGROUND

Although iodine modulates bone metabolism in the treatment of thyroid disease, the effect of iodine intake on bone metabolism remains less known.

OBJECTIVE

This study evaluated the effect of excess iodine intake in rats on bone reconstruction in the 6th and 12th month of intervention.

METHOD

Rats were treated with different doses of iodinated water: the normal group (NI, 6.15 μg/d), 5-fold high iodine group (5HI, 30.75 μg/d), 10-fold high iodine group (10HI, 61.5 μg/d), 50-fold high iodine group (50HI, 307.5 μg/d), and 100-fold high iodine group (100HI, 615 μg/d). Thyroid hormone concentrations were determined by a chemiluminescent immunoassay. Morphometry and microstructure of bone trabecula were observed by hematoxylin and eosin staining and microcomputed tomography, respectively. Alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate the activity of osteoblasts and osteoclasts, respectively.

RESULTS

The 24-h urine iodine concentration increased with iodine intake. The rats in the HI groups had higher serum thyroid-stimulating hormone and decreased serum free thyroxine concentrations in the 12th month than the NI group (all P < 0.05). The percentage of the trabecular bone area and osteoblast perimeter in the 100HI group were significantly lower than those in the NI group (P < 0.05). Increased structure model index was observed in the 50HI and 100HI groups compared with the NI group in the 6th month and increased trabecular separation in the 12th month (all P < 0.05). ALP and TRAP staining revealed osteoblastic bone formation was reduced, and the number of TRAP+ multinucleated cells decreased with increasing iodine intake.

CONCLUSIONS

Excess iodine intake may increase the risk of hypothyroidism in rats. Chronic excess iodine intake can lead to abnormal changes in skeletal structure, resulting in reduced activity of osteoblasts and osteoclasts, which inhibits the process of bone reconstruction and may lead to osteoporosis.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

Emerging research themes in maternal hypothyroidism: a bibliometric exploration

Background

Hypothyroidism, a prevalent endocrine disorder, carries significant implications for maternal and infant health, especially in the context of maternal hypothyroidism. Despite a gradual surge in recent research, achieving a comprehensive understanding of the current state, focal points, and developmental trends in this field remains challenging. Clarifying these aspects and advancing research could notably enhance maternal-infant health outcomes. Therefore, this study employs bibliometric methods to systematically scrutinize maternal hypothyroidism research, serving as a reference for further investigations.

Objective

Through bibliometric analysis, this study seeks to unveil key research focus areas, developmental trends, and primary contributors in Maternal Hypothyroidism. The findings offer insights and recommendations to inform future research endeavors in this domain.

Methods

Literature metrics analysis was performed on data retrieved and extracted from the Web of Science Core Collection database. The analysis examined the evolution and thematic trends of literature related to Maternal Hypothyroidism. Data were collected on October 28, 2023, and bibliometric analysis was performed using VOSviewer, CiteSpace, and the Bibliometrix software package, considering specific characteristics such as publication year, country/region, institution, authorship, journals, references, and keywords.

Results

Retrieved from 1,078 journals, 4,184 articles were authored by 18,037 contributors in 4,580 institutions across 113 countries/regions on six continents. Maternal Hypothyroidism research publications surged from 44 to 310 annually, a 604.54% growth from 1991 to 2022. The USA (940 articles, 45,233 citations), China Medical University (82 articles, 2,176 citations), and Teng, Weiping (52 articles, 1,347 citations) emerged as the most productive country, institution, and author, respectively. "Thyroid" topped with 233 publications, followed by "Journal of Clinical Endocrinology & Metabolism" (202) with the most citations (18,513). "Pregnancy" was the most cited keyword, with recent high-frequency keywords such as "outcome," "gestational diabetes," "iodine intake," "preterm birth," "guideline," and "diagnosis" signaling emerging themes in Maternal Hypothyroidism.

Conclusions

This study unveils developmental trends, global collaboration patterns, foundational knowledge, and emerging frontiers in Maternal Hypothyroidism. Over 30 years, research has predominantly focused on aspects like diagnosis, treatment guidelines, thyroid function during pregnancy, and postpartum outcomes, with a central emphasis on the correlation between maternal and fetal health.

Are there bidirectional associations between maternal thyroid function and glucose metabolism in singleton live births? A birth cohort study

(1) Aims: To examine the associations between maternal thyroid function and glucose metabolism during pregnancy. (2) Methods: This study was based on Ma' anshan Birth Cohort in China. Totally 2375 pregnant women were included in data analysis. Maternal thyroid-stimulating hormone (TSH), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb) and fasting plasma glucose (FPG) levels during the first, second and third trimesters of pregnancy were measured retrospectively. Mplus 8.0 was used to construct a cross-lagged panel model to examine the potential bidirectional association between thyroid function and FPG levels throughout pregnancy. (3) Results: FT4 levels were positively correlated with FPG levels in the first trimester and negatively correlated with FPG levels in the second trimester. TSH levels were negatively associated with FPG levels in the second trimester, and in the first trimester, it could positively predict FPG levels in the second trimester. No significant association was found between TPOAb levels and FPG levels during pregnancy. (4) Conclusions: There was a non-bidirectional association between maternal thyroid function and glucose metabolism during pregnancy. FT4 and TSH levels influence FPG concentrations in the first and second trimesters of pregnancy.

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.

Mechanism of multi-organ compensation under different iodine intake in pregnant rats: results from a repeated-measures study of iodine metabolism

PURPOSE

This study aimed to explore the differences in iodine metabolism and expression of NIS and Pendrin in pregnant rats under different iodine nutritional status.

METHODS

Female Wistar rats were divided into four groups: low iodine (LI), normal iodine (NI), ten fold high iodine (10HI), and fifty fold high iodine (50HI). The intervention began after one week of adaptive feeding. Iodine metabolism experiments were performed beginning on the 15th day of pregnancy. 24-h iodine intake and excretion were calculated. The concentrations of iodine in urine, fecal, thyroid, and placenta were measured by ICP-MS. PCR and Western Blot were used to detect the mRNA levels and cell membrane protein of sodium/iodide symporter (NIS) and Pendrin in the small intestine, thyroid, kidney, and placenta.

RESULTS

Fecal iodine excretion (FIE) and urinary iodine excretion (UIE) in the 50HI group were significantly higher than those in the NI group (P < 0.05). The NIS protein and mRNA in the kidney and small intestine have an upward trend in iodine deficiency and a downward trend in iodine excess. Thyroid and placental iodine storage in the 50HI group were significantly higher than those in the NI group (P < 0.05). NIS, Pendrin protein, and mRNA in the thyroid and placenta tend to increase when iodine is deficient and decrease when there is excess.

CONCLUSION

Iodine excretion and iodine stores in the placenta and thyroid gland are positively correlated with iodine intake. NIS and Pendrin are also regulated by iodine intake.

Cellular Iron Deficiency Disrupts Thyroid Hormone Regulated Gene Expression in Developing Hippocampal Neurons

BACKGROUND

Developing neurons have high thyroid hormone and iron requirements to support their metabolically demanding growth. Early-life iron and thyroid-hormone deficiencies are prevalent and often coexist, and each independently increases risk of permanently impaired neurobehavioral function in children. Early-life dietary iron deficiency reduces thyroid-hormone concentrations and impairs thyroid hormone-responsive gene expression in the neonatal rat brain, but it is unclear whether the effect is cell-intrinsic.

OBJECTIVES

This study determined whether neuronal-specific iron deficiency alters thyroid hormone-regulated gene expression in developing neurons.

METHODS

Iron deficiency was induced in primary mouse embryonic hippocampal neuron cultures with the iron chelator deferoxamine (DFO) beginning at 3 d in vitro (DIV). At 11DIV and 18DIV, thyroid hormone-regulated gene messenger ribonucleic acid (mRNA)concentrations indexing thyroid hormone homeostasis (Hairless, mu-crystallin, Type II deiodinase, solute carrier family member 1c1, and solute carrier family member 16a2) and neurodevelopment (neurogranin, Parvalbumin, and Krüppel-like factor 9) were quantified. To assess the effect of iron repletion, DFO was removed at 14DIV from a subset of DFO-treated cultures, and gene expression and adenosine 5'-triphosphate (ATP) concentrations were quantified at 21DIV.

RESULTS

At 11DIV and 18DIV, neuronal iron deficiency decreased neurogranin, Parvalbumin, and mu-crystallin, and by 18DIV, solute carrier family member 16a2, solute carrier family member 1c1, Type II deiodinase, and Hairless were increased, suggesting cellular sensing of a functionally abnormal thyroid hormone state. Dimensionality reduction with Principal component analysis reveals that thyroid hormone homeostatic genes strongly correlate with and predict iron status. Iron repletion from 14-21DIV did not restore ATP concentration, and Principal component analysis suggests that, after iron repletion, cultures maintain a gene expression signature indicative of previous iron deficiency.

CONCLUSIONS

These novel findings suggest there is an intracellular mechanism coordinating cellular iron/thyroid hormone activities. We speculate this is a part of the homeostatic response to acutely match neuronal energy production and growth signaling. However, the adaptation to iron deficiency may cause permanent deficits in thyroid hormone-dependent neurodevelopmental processes even after recovery from iron deficiency.

A Cohort Study on the Effects of Maternal High Serum Iodine Status During Pregnancy on Infants in Terms of Iodine Status and Intellectual, Motor, and Physical Development

The objective of the present study was to explore the effects of maternal iodine excess during pregnancy on infants' neurodevelopment and physical development. A total of 143 mother-child pairs were enrolled in this cohort study. Maternal blood samples were collected during the obstetric examination. A mother-child questionnaire survey was conducted, and infants' blood samples were collected during the newborn physical examination. Infants' single-spot urine samples were collected, and intellectual, motor, and physical development were assessed at 2 months of age. The median (IQR) maternal serum iodine concentrations (SICs) in the first, second, and third trimesters of pregnancy were 91.2 (74.4, 102.2) μg/L, 81.2 (70.6, 94.8) μg/L, and 82.0 (68.9, 100.3) μg/L, respectively. In the first trimester of pregnancy, infants' psychomotor developmental index (PDI), body mass index (BMI) and weight-for-length Z score (WLZ) were higher with maternal suitable SIC (40 ~ 92 μg/L) than with maternal excess SIC (P < 0.05). Infants' PDI, BMI, weight-for-age Z score (WAZ) and WLZ were negatively correlated with maternal SIC (P < 0.05). Maternal excess SIC had a slightly negative effect on infants' MDI (OR = 1.304, P = 0.035, 95% CI = 1.019 ~ 1.668), PDI (OR = 1.124, P = 0.001, 95% CI = 1.052 ~ 1.200) and BMI (OR = 0.790, P = 0.005, 95% CI = 0.669 ~ 0.933). In the third trimester, infants' length-for-age Z score (LAZ) was higher with maternal high SIC (> 92 μg/L) (P = 0.015), and maternal SIC was positively correlated with infants' urine iodine concentration (UIC) (P = 0.026). Maternal iodine excess in the first trimester had a slightly negative effect on infants' intellectual, motor, and physical development. In the third trimester, maternal iodine excess only may have a positive impact on infants' height. Additionally, maternal iodine status was closely related to infants' iodine status.

Iodine: a scoping review for Nordic Nutrition Recommendations 2023

Iodine is essential for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). As in many other parts of the world, insufficient iodine intake and consequently insufficient iodine status is a public health challenge in the Nordic and Baltic countries. The main dietary sources of iodine in the Nordic and Baltic countries include cow's milk, saltwater fish, eggs, products containing iodised salt, and iodised table salt. Only Denmark (DK), Finland (FI) and Sweden (SE) have implemented mandatory (DK) or voluntary (SE, FI) salt iodisation. New data, as well as recent studies from the Nordic and Baltic countries, strengthen the evidence that the main health challenges related to insufficient iodine intake remain thyroid function and thyroid disease, mental development, and cognitive function. Excessive intakes can also cause hyperthyroidism, autoimmune thyroid disease, and thyroid cancer.

Serum iodine concentration and its associations with thyroid function and dietary iodine in pregnant women in the southeast coast of China: a cross-sectional study

Background

Iodine deficiency is a major public health problem in pregnant women. Serum iodine (SI) may represent a useful biomarker for iodine nutrition evaluation. We aimed to assess the relationship between serum iodine concentration (SIC) and urinary iodine concentration (UIC), dietary iodine, thyroid function, and thyroid diseases in pregnant women in the southeast coast of China, and to provide a normal reference range of SIC for pregnant women.

Methods

A multistage random sampling method was used to select the study population. We collected urine and blood samples from pregnant women and determined UIC and SIC as well as thyroid function using Arsenic-Cerium Catalytic Spectrophotometry, inductively coupled plasma mass spectrometry, and Beckman Coulter Access2 chemiluminescent immunoanalyzer and kit, respectively, and administered a questionnaire on dietary iodine intake in pregnant women.

Results

There was a significant negative correlation between SI and thyroid-stimulating hormone (TSH) (r = -0.141) and a significant positive correlation between SI and free triiodothyronine (FT3) (r = 0.106), free thyroxine (FT4) (r = 0.236), triiodothyronine (TT3) (r = 0.229), total thyroxine (TT4) (r = 0.433), and dietary iodine intake (r = 0.068). There was a significant difference in SI levels of pregnancy between the second (78.13 μg/L) and third trimester (75.37 μg/L) (p = 0.018). SI levels between inadequate intake (74.58 μg/L) and appropriate intake (77.92 μg/L) groups were statistically different (p = 0.036). Low SIC was a risk factor for the development of hypothyroxinemia (adjusted OR = 3.14, 95% confidence interval: 1.75-5.66). The reference range for SIC in normal pregnant women is 45.03-112.44 μg/L.

Conclusion

SI may be a composite indicator of iodine nutritional status and thyroid function.

Re-exploration of dietary iodine intake in Chinese adult males using a modified iodine balance study

There is still controversy about optimal dietary iodine intake as the Universal Salt Iodization policy enforcement in China. A modified iodine balance study was thus conducted to explore the suitable iodine intake in Chinese adult males using the iodine overflow hypothesis. In this study, thirty-eight apparently healthy males (19·1 (sd 0·6) years) were recruited and provided with designed diets. After the 14-d iodine depletion, daily iodine intake gradually increased in the 30-d iodine supplementation, consisting of six stages and each of 5 d. All foods and excreta (urine, faeces) were collected to examine daily iodine intake, iodine excretion and the changes of iodine increment in relation to those values at stage 1. The dose-response associations of iodine intake increment with excretion increment were fitted by the mixed effects models, as well as with retention increment. Daily iodine intake and excretion were 16·3 and 54·3 μg/d at stage 1, and iodine intake increment increased from 11·2 μg/d at stage 2 to 118·0 μg/d at stage 6, while excretion increment elevated from 21·5 to 95·0 μg/d. A zero iodine balance was dynamically achieved as 48·0 μg/d of iodine intake. The estimated average requirement and recommended nutrient intake were severally 48·0 and 67·2 μg/d, which could be corresponded to a daily iodine intake of 0·74 and 1·04 μg/kg per d. The results of our study indicate that roughly half of current iodine intakes recommendation could be enough in Chinese adult males, which would be beneficial for the revision of dietary reference intakes.

Ambient particulate matter, maternal thyroid function, and birth weight: A mediation analysis

BACKGROUND

Birth weight (BW) is an indicator of fetal growth and development. Previous studies showed inconsistent results on the association of ambient particulate matter (PM) exposure with BW, and the role of maternal thyroid function has not been clarified.

METHODS

We recruited 1711 gravidas between 2017 and 2019 in Henan, China. All participants were followed up until delivery. Daily concentrations of PM, including PM2.5 and PM10, were evaluated by using the spatial-temporal model. Maternal thyroid hormone (TH) levels were quantified by electrochemiluminescent microparticle immunoassay. Linear regression models were employed to examine the association among PM, BW, and maternal TH. Mediating effects of maternal TH interrelated with PM exposure on BW were investigated by causal mediation analyses.

RESULTS

A total of 1049 gravidas were identified. We found that per 10 µg/m3 increase in PM2.5 and PM10 were associated with a decreased BW of 9.941 g, and 7.758 g (PM2.5: 95 %CI: -18.184, -1.698; PM10: 95 %CI: -14.436, -1.080). An inverse correlation of maternal FT4 levels with BW was found, with the pooled β of -319.983 g (95 %CI: -483.216, -156.750). We found a prominent positive correlation between gestational FT4 and PM exposure (PM2.5: β = 0.004, 95 %CI: 0.001, 0.007; PM10: β = 0.003, 95 %CI: 0.000, 0.006). Mediation analysis found that FT4 levels mediated the relationship between maternal PM exposure and BW, ranging from 5.55 % to 15.86 %.

CONCLUSIONS

Maternal PM exposure may induce a reduction in newborn BW by affecting the maternal TH concentrations.

Iodine-induced thyroid dysfunction: a scientometric study and visualization analysis

Objective

Iodine is essential in thyroid hormone production. Iodine deficiency is associated with serious complications (i.e miscarriage and stillbirth), whereas excess can cause thyroid dysfunction (i.e hyperthyroidism, hypothyroidism, thyroid autoimmunity). We conducted this scientometric study to visualize hot spots and trends in iodine-induced thyroid dysfunction over past two decades. The aim of this paper was to help scholars quickly understand the development and potential trend in this field, and guide future research directions.

Methods

Articles on iodine-induced thyroid dysfunction from 2000 to 2022 were retrieved from the Web of Science Core Collection (WoSCC) using the following search terms: (((((TS=(hypothyroid*)) OR TS=(hyperthyroid*)) OR TS= ("TSH deficiency")) OR TS= ("thyroid stimulating hormone deficiency")) AND TS=(Iodine)) NOT TS=(radioiodine). Only publications in English were selected. CiteSpace, VOSviewer, Tableau, Carrot2, and R software were used to analyze the contribution and co-occurrence relationships of different countries, institutes, keywords, references, and journals.

Results

A total of 2986 publications from 115 countries and 3412 research institutions were included. From 2000 to 2022, research on iodine-induced thyroid dysfunction progressed over a three-stage development period: initial development (2000-2009), stable development (2010-2016), and rapid development (2016-2022) period. The Journal of Clinical Endocrinology and Metabolism had the most co-citations followed and China Medical University (n=76) had the most publications. The top three clusters of co-citation references were isolated maternal hypothyroxinemia, subclinical hyperthyroidism, and brain development. Various scientific methods were applied to reveal acknowledge structure, development trend and research hotspots in iodine-induced thyroid dysfunction.

Conclusion

Our scientometric analysis shows that investigations related to pregnant women, epidemiology surveys, and iodine deficiency are promising topics for future iodine-induced thyroid dysfunction research and highlights the important role of iodine on thyroid function.

Effectiveness of iodine for continuous decontamination of dental unit waterline

OBJECTIVE

Dental Unit Waterlines (DUWLs) are contaminated by various species of microorganisms. DUWLs should be disinfected appropriately to control microbial contamination. This study investigated the effectiveness of devices continuously releasing iodine to control microbial contamination in DUWLs.

MATERIALS AND METHODS

Ten dental chair units (DCU) at Chulalongkorn University were randomized into the iodine and control groups. After setting iodine treatment devices, the DCU was allowed to operate normally. 25 ml of water from airotors lines were collected weekly for enumerating bacteria. The viability of biofilms in DUWLs was quantified by ATP testing kit. The amount of iodine released into the procedural water was also quantified.

RESULTS

The continuous presence of iodine could significantly control bacterial contamination in the DUWL to be less than 500 CFU/mL, the standard level recommended by the Centre for Disease Control and Prevention (CDC). Iodine treatment can reduce bacterial CFU up to 98-100%. Biofilm viability in the iodine group was slightly lower than that of the control group though not statistically significant. After eleven months, the average iodine release was measured to be 3.6 ppm which is still effective in controlling bacterial contamination.

CONCLUSION

Continuously supplying iodine in DUWLs effectively controls microbial contamination.

Urinary iodine concentration and its associations with thyroid function in pregnant women of Shanghai

Objective

To assess the iodine status and its associations with thyroid function in pregnant women of Shanghai.

Methods

In this cross-sectional study, a total of 562 pregnant women were enrolled from January to December 2021. Both serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), thyroid peroxidase antibody (TPOAB), thyroglobulin antibody (TGAB), and urinary iodine concentration (UIC) were detected. Participants were divided into four groups based on their UIC values. Correlation analysis was used to investigate the association between UIC and thyroid function-associated parameters.

Results

The median UIC of the pregnant women studied was 158.25µg/L (interquartile range [IQR] 90.15, 245.65µg/L). Among all the subjects, 45.55% had iodine deficiency according to the World Health Organization (WHO) criteria, and 15.65% had thyroid autoimmunity. FT3, FT4, TSH, TPOAB and TGAB levels were not different among different UIC groups (P > 0.05). UIC and TSH were negatively correlated (r=-0.127, p=0.043) in UIC<150 µg/L group. In the group with UIC 250- 499 µg/L, UIC was positively correlated with total T4 (TT4), total T3 (TT3) and TPOAB (r= 0.228, p=0.022, r=0.208, p= 0.039, r=0.190, p=0.042, respectively). A negative correlation between UIC and TPOAB values was observed in TPOAB-positive (+) pregnant women (r=-0.384, p=0.012). The prevalence of isolated hypothyroxinemia in UIC<150 µg/L group was significantly higher than that of other groups(p=0.033). The relationship between the prevalence of thyroid diseases and UIC embodied a U-shaped curve.

Conclusion

Pregnant women on Chongming Island of Shanghai were iodine sufficient during the second trimester, but iodine deficiency was still prevalent. Both low and high gestational iodine status was related to thyroid function and autoimmunity. Optimal iodine nutrition status during gestation was important.

Relationship between iodine knowledge and dietary iodine intake in pregnant and lactating women: a cross-sectional study

OBJECTIVE

This study assessed the iodine knowledge of pregnant and lactating women and the relationship to dietary iodine intake and iodine status. The factors influencing iodine intake were analysed.

DESIGN

Basic information and iodine knowledge were collected via a questionnaire. A FFQ assessed dietary iodine intake. The urinary iodine concentration (UIC) was measured using the arsenic-cerium catalytic spectrophotometric determination of iodine in urine (WS/T 107 -2016).

SETTING

A cross-sectional study involving pregnant and lactating women in Xinjiang, China was conducted.

PARTICIPANTS

A total of 1181 pregnant women and 504 lactating women were enrolled in the study.

RESULTS

The median UIC for pregnant and lactating women was 179·27 and 192·81 µg/l, respectively, and the dietary iodine intake was 407·16 and 356·89 µg/d, respectively. Of the pregnant and lactating women, 73·4 % and 82·5 % had medium iodine knowledge, respectively. In pregnant women, iodine knowledge and dietary iodine intake were positively correlated. High iodine knowledge and iodine education were shown to be protective factors for excessive iodine intake in pregnant women.

CONCLUSION

This study demonstrated that the iodine nutritional status of women in Xinjiang was appropriate, and iodine knowledge was at a medium level, but there was confusion about iodine nutrition. Public education is needed to improve iodine knowledge and active iodine supplementation awareness among these populations of women.

Associations of Maternal Serum Iodine Concentration with Obstetric Complications and Birth Outcomes-Longitudinal Analysis Based on the Huizhou Mother-Infant Cohort, South China

This study aimed to explore the temporal associations between maternal serum iodine concentration (SIC) and common pregnancy outcomes in Chinese women. Eligible singleton pregnant women aged 20-34 years were selected, and their fasting blood samples were collected during early (T1, n = 1101) and mid-pregnancy (T2, n = 403) for SIC testing by inductively coupled plasma mass spectrometry. Multivariable linear regression indicated that log₁₀SIC at T1 (β = -0.082), T2 (β = -0.198), and their % change (β = -0.131) were inversely associated with gestational weight gain (GWG, all p < 0.05). Maternal log₁₀SIC at both T1 (β = 0.077) and T2 (β = 0.105) were positively associated with the Apgar score at 1 min (both p < 0.05). Women in the third quartile (Q3) of SIC at T1 had a lower risk of small for gestational age (SGA, OR = 0.405, 95% CI: 0.198-0.829) compared with those in Q4. Restricted cubic spline regression suggested a U-shaped association between SIC and SGA risk, and SIC above 94 μg/L at T1 was the starting point for an increased risk of SGA. The risk of premature rupture of membrane (PROM) increased by 96% (OR = 1.960, 95% CI: 1.010-3.804) in Q4 compared to that in Q1. Our longitudinal data from an iodine-replete region of China indicated that high maternal SIC could restrict GWG and improve Apgar scores at delivery, but might increase the risk of SGA and PROM.

Cellular Iron Deficiency Disrupts Thyroid Hormone Regulated Gene Expression in Developing Hippocampal Neurons

Background

Developing neurons have high thyroid hormone and iron requirements to support their metabolism and growth. Early-life iron and thyroid hormone deficiencies are prevalent, often coexist, and increase the risk of permanently impaired neurobehavioral function in children. Early-life dietary iron deficiency reduces thyroid hormone levels and impairs thyroid hormone-responsive gene expression in the neonatal rat brain.

Objective

This study determined whether neuronal-specific iron deficiency alters thyroid hormone-regulated gene expression in developing neurons.

Methods

Iron deficiency was induced in primary mouse embryonic hippocampal neuron cultures with the iron chelator deferoxamine (DFO) beginning at 3 days in vitro (DIV). At 11DIV and 18DIV, mRNA levels for thyroid hormone-regulated genes indexing thyroid hormone homeostasis (Hr, Crym, Dio2, Slco1c1, Slc16a2) and neurodevelopment (Nrgn, Pvalb, Klf9) were quantified. To assess the effect of iron repletion, DFO was removed at 14DIV from a subset of DFO-treated cultures and gene expression and ATP levels were quantified at 21DIV.

Results

At 11DIV and 18DIV, neuronal iron deficiency decreased Nrgn, Pvalb, and Crym, and by 18DIV, Slc16a2, Slco1c1, Dio2, and Hr were increased; collectively suggesting cellular sensing of a functionally abnormal thyroid hormone state. Dimensionality reduction with Principal Component Analysis (PCA) reveals that thyroid hormone homeostatic genes strongly correlate with and predict iron status (Tfr1 mRNA). Iron repletion from 14-21DIV restored neurodevelopmental genes, but not all thyroid hormone homeostatic genes, and ATP concentrations remained significantly altered. PCA clustering suggests that cultures replete with iron maintain a gene expression signature indicative of previous iron deficiency.

Conclusions

These novel findings suggest there is an intracellular mechanism coordinating cellular iron/thyroid hormone activities. We speculate this is a part of homeostatic response to match neuronal energy production and growth signaling for these important metabolic regulators. However, iron deficiency may cause permanent deficits in thyroid hormone-dependent neurodevelopmental processes even after recovery from iron deficiency.

Iodine Metabolism and Thyroid Function During the Perinatal Period: Maternal-Neonatal Correlation and Effects of Topical Povidone-Iodine Skin Disinfectants

An adequate maternal iodine intake during pregnancy and lactation is essential for growth and mental development in fetuses and newborns. There are limited data on perinatal iodine metabolism in mothers and infants, as well as the effect of povidone-iodine (PVP-I) antiseptics used in cesarean delivery. The urinary iodine concentration (UIC), serum iodine, thyrotropin (TSH), free thyroxine (FT4), and breast milk iodine concentration (BMIC) were measured consecutively in a total of 327 mothers and 249 term-infants in two prospective studies. The maternal median UIC was 164 μg/L in the third trimester, increased to 256 μg/L at 44 h after birth, and then decreased to 116 μg/L 1 month later. The BMIC on the 4th and 32th postpartum days was 17.6 and 13.5 μg/100 g, respectively. In neonatal infants born to the mothers unexposed to PVP-I, the median UIC was 131 μg/L in the first voiding urine and increased to 272 μg/L on day 4 and then slightly decreased to 265 μg/L on day 28 suggesting sufficient iodine reserve at birth. PVP-I antiseptics containing 1 g of iodine for skin preparation at cesarean delivery transiently increased maternal serum iodine concentration (1.9-fold), UIC (7.8-fold) at 41 h after surgery and BMIC, while it had little effect on maternal TSH, FT4, and neonatal UIC, TSH, or FT4. The iodine status of pregnant women and their infants was adequate in this population; however, the UIC in lactating mothers at one postpartum month was low enough to suggest iodine deficiency or near iodine deficiency. Further studies are necessary.

Iodine Deficiency, Maternal Hypothyroxinemia and Endocrine Disrupters Affecting Fetal Brain Development: A Scoping Review

This scoping review critically discusses the publications of the last 30 years on the impact of mild to moderate iodine deficiency and the additional impact of endocrine disrupters during pregnancy on embryonal/fetal brain development. An asymptomatic mild to moderate iodine deficiency and/or isolated maternal hypothyroxinemia might affect the development of the embryonal/fetal brain. There is sufficient evidence underlining the importance of an adequate iodine supply for all women of childbearing age in order to prevent negative mental and social consequences for their children. An additional threat to the thyroid hormone system is the ubiquitous exposure to endocrine disrupters, which might exacerbate the effects of iodine deficiency in pregnant women on the neurocognitive development of their offspring. Ensuring adequate iodine intake is therefore essential not only for healthy fetal and neonatal development in general, but it might also extenuate the effects of endocrine disruptors. Individual iodine supplementation of women of childbearing age living in areas with mild to moderate iodine deficiency is mandatory as long as worldwide universal salt iodization does not guarantee an adequate iodine supply. There is an urgent need for detailed strategies to identify and reduce exposure to endocrine disrupters according to the "precautional principle".

Adverse Effects on the Thyroid of Chinese Pregnant Women Exposed to Long-Term Iodine Excess: Optimal and Safe Tolerable Upper Intake Levels of Iodine

Ensuring optimal iodine nutrition in pregnant women is a global public health concern. However, there is no direct data on safe tolerable upper intake levels (ULs) for pregnant women. A cross-sectional study was performed to determine the ULs of pregnant women. A total of 744 pregnant women were enrolled in this study. The median (IQR) urinary iodine concentration (UIC) in pregnant women was 150.2 (87.6, 268.0) μg/L, and the urinary iodine excretion (UIE) over 24 h was 204.2 (116.0, 387.0) μg/day. Compared with those with a UIE figure of between 150–250 μg/day, the reference group, the prevalence of thyroid dysfunction was 5.7 times higher (95%CI: 1.7, 19.2) in pregnant women with a UIE figure of between 450–550 μg/day, and 3.9 times higher (95%CI: 1.5, 10.3) in pregnant women with a UIE figure of ≥550 μg/day. Compared with an estimated iodine intake (EII) of between 100–200 μg/day, the reference group, the prevalence of thyroid dysfunction was 4.3 times higher (95%CI: 1.3, 14.4) in pregnant women with a UIE figure of between 500–600 μg/day, and 3.6 times higher (95%CI: 1.5, 8.9) in pregnant women with UIE of ≥600 μg/day. In general, our cross-sectional study found that excessive iodine intake during pregnancy appears to directly increase the risk of thyroid dysfunction. Avoiding chronic iodine intakes of 500 μg/day or higher or having a UIE figure of ≥450 μg/day is recommended for pregnant women in China.

Invited review: Iodine level in dairy products-A feed-to-fork overview

The theme of iodine in the dairy sector is of particular interest due to the involvement and the interconnection of several stakeholders along the dairy food chain. Iodine plays a fundamental role in animal nutrition and physiology, and in cattle it is an essential micronutrient during lactation and for fetal development and the calf's growth. Its correct use in food supplementation is crucial to guarantee the animal's recommended daily requirement to avoid excess intake and long-term toxicity. Milk iodine is fundamental for public health, being one of the major sources of iodine in Mediterranean and Western diets. Public authorities and the scientific community have made great efforts to address how and to what extent different drivers may affect milk iodine concentration. The scientific literature concurs that the amount of iodine administered through animal feed and mineral supplements is the most important factor affecting its concentration in milk of most common dairy species. Additionally, farming practices related to milking (e.g., use of iodized teat sanitizers), herd management (e.g., pasture vs. confinement), and other environmental factors (e.g., seasonality) have been identified as sources of variation of milk iodine concentration. Overall, the aim of this review is to provide a multilevel overview on the mechanisms that contribute to the iodine concentration of milk and dairy products.

Gestational thyroid hormone concentrations and risk of attention-deficit hyperactivity disorder in the Norwegian Mother, Father and Child Cohort Study

BACKGROUND

Maternal thyroid function plays an important role in foetal brain development; however, little consensus exists regarding the relationship between normal variability in thyroid hormones and common neurodevelopmental disorders, such as attention-deficit hyperactivity disorder (ADHD).

OBJECTIVE

We sought to examine the association between mid-pregnancy maternal thyroid function and risk of clinically diagnosed ADHD in offspring.

METHODS

We conducted a nested case-control study in the Norwegian Mother, Father and Child Cohort Study. Among children born 2003 or later, we randomly sampled singleton ADHD cases obtained through linkage with the Norwegian Patient Registry (n = 298) and 554 controls. Concentrations of maternal triiodothyronine (T3), thyroxine (T4), T3-Uptake, thyroid-stimulating hormone (TSH) and thyroid peroxidase antibody (TPO-Ab) were measured in maternal plasma, collected at approximately 17 weeks' gestation. Indices of free T4 (FT4i) and free T3 (FT3i) were calculated. We used multivariable adjusted logistic regression to calculate odds ratios and accounted for missing covariate data using multiple imputation. We used restricted cubic splines to assess non-linear trends and provide flexible representations. We examined effect measure modification by dietary iodine and selenium intake. In sensitivity analyses, we excluded women with clinically significant thyroid disorders (n = 73).

RESULTS

High maternal T3 was associated with increased risk of ADHD (5th vs 1st quintile odds ratio  2.27, 95% confidence interval 1.21, 4.26). For FT4i, both the lowest and highest quintiles were associated with an approximate 1.6-fold increase in risk of ADHD, with similar trends found for T4. The FT4i association was modified by dietary iodine intake such that the highest risk strata were confined to the low intake group.

CONCLUSIONS

Both high and low concentrations of maternal thyroid hormones, although within population reference ranges, increase the risk of ADHD in offspring. Increased susceptibility may be found among women with low dietary intake of iodine and selenium.

Iodine status in pregnant women in northern Spain. Effect of iodised salt and iodine supplements on thyroid function

INTRODUCTION

Iodine deficiency is linked to thyroid dysfunction, particularly in pregnant women. The objective of this study was to ascertain the iodine levels of women in the second trimester of pregnancy, analysing the influence of iodine ingestion on urinary iodine concentration (UIC) and maternal thyroid function.

METHODS

A prospective observational study of pregnant women from Health Area IV of Asturias (northern Spain) recruited before 13 weeks of gestation between May and June 2017. A questionnaire on iodine intake was completed at the first visit, and urine and serum samples were collected at baseline and again during the second trimester. UIC, thyroid stimulating hormone (TSH) and free thyroxine (FT4) obtained in the second trimester of gestation were analysed and related to iodine intake. Thyroid autoimmunity was also analysed in half of the pregnant women at baseline.

RESULTS

A total of 241 pregnant women were studied. Of these, 56.7% used iodised salt, 46.7% consumed ≥2 servings of dairy products daily and 88.1% took iodine supplements. Median UIC was 191μg/l (135.3-294μg/l), with 68.1% of the women having UIC ≥150μg/l. Only iodised salt consumption provided protection against iodine deficiency (odds ratio 0.35 [0.20-0.63], p=0.001). In women with no autoimmune thyroid disease (n=88), mean levels of TSH were lower in those that consumed iodised salt than in those that did not (respectively, 2.08±0.89mIU/l vs. 2.56±1.02mIU/l, p=0.025). In women with autoimmune thyroid disease (n=30), mean levels of TSH were higher in those that took iodine supplements than in those that did not (respectively, 2.97±1.25mIU/l vs. 1.16±0.41mIU/l, p=0.002).

CONCLUSIONS

The pregnant women studied from Health Area IV in Asturias maintain adequate nutritional iodine status in the second trimester of gestation. In our sample, only the consumption of iodised salt was associated with adequate iodine nutrition, without affecting maternal thyroid function. Most of the women used iodine supplements, which was linked to higher levels of TSH in pregnant women with autoimmune thyroid disease.

Iodide Excess Inhibits Thyroid Hormone Synthesis Pathway Involving XBP1-Mediated Regulation

Iodine is an essential micronutrient for producing thyroid hormone (TH); however, iodide excess can lead to adverse thyroidal effects. Unfortunately, the lack of a proper in vitro model system hampered the studies of the effect of iodide excess on thyroid physiology and pathology. Here, we demonstrated that excessive iodide intake downregulated the genes related to TH synthesis in the thyroids of mice. Since sodium iodide has no effect on these genes in cultured cell lines, we developed a three-dimensional (3D) culture system to enable the murine thyrocytes to form organoids in vitro with thyroid follicle-like structures and function and found that the in vivo effect of iodide excess could be mimicked in these thyroid organoids. Our data indicate that iodide excess mainly activated the XBP1-mediated unfolded protein response in both murine thyroid and thyroid organoids, while activation of XBP1 was able to mimic the sodium iodide effect on genes for the synthesis of TH in murine thyroid organoids. Lastly, our results suggest that XBP1 might transcriptionally repress the genes involved in the synthesis of TH. Based on these findings, we propose that iodide excess inhibits the transcription of genes related to TH synthesis through a mechanism involving XBP1-mediated action.

A Narrative Review on the Effect of Maternal Hypothyroidism on Fetal Development

The thyroid is a butterfly-shaped gland located in the human body's neck region. The thyroid produces three hormones that are essential for regulating body temperature, energy production, weight, hair and nail growth, and menstrual cycle maintenance. The production of these hormones is controlled by a feedback mechanism. Various factors cause changes in the stimulation and inhibition of these hormones, which ultimately causes either excessive release or a decrease in the levels of thyroid hormones. These causes can be physiological or pathological. One of the physiological causes is pregnancy. Pregnancy is a very complex process in which many changes occur in the body and its functioning. One of which is changes in the maternal thyroid gland. The inability to adequately adapt to the changes leads to the abnormal functioning of the thyroid gland. During pregnancy, there is a variation in the concentration of thyroid hormones which may cause a decrease in levels or inhibition in the production of thyroid hormones. This condition is called hypothyroidism. Hypothyroidism in pregnant mothers can either be gestational or may be a condition that is present way before her pregnancy. Often, gestational hypothyroidism reverts after delivery during the postpartum period but can also be present as subclinical hypothyroidism. In such cases, they pose a significant threat to development, cause growth hindrance to the infant in the womb, and cause abnormalities in the offspring in the future. Some of the changes occur in the gland because of enhancement in levels of thyroid binding globulin, increased clearance rate of iodine from the body in kidneys, altered effects in human chorionic gonadotropin hormone, and decreased consumption of iodine in meals. Iodine disbalance in maternal hypothyroidism is associated with severe health issues like cretinism and mental retardation. Thyroid hormones are crucial for the infant's neural, cognitive, and intelligence quotient development in the womb. Thus, the disturbances in the maternal hormone levels disturb typical early developmental characteristics. In the world of rapidly advancing scientific research, there are many ways in which this condition can be detected early, diagnosed correctly, and given apt and required attention and treatment for causing the least harm to the fetus and the mother.

High intakes of iodine among women during pregnancy and the postpartum period has no adverse effect on thyroid function

PURPOSE

Given the high consumption of seaweed soup by pregnant and lactating Korean women, concerns have been raised about excessive iodine intake. We evaluated the effects of maternal iodine intake on maternal thyroid function and birth outcomes. We also evaluated iodine intake via seaweed soup during late pregnancy and the early postpartum period.

METHODS

A total of 349 pregnant women of the Ideal Breast Milk cohort were recruited in late pregnancy, of whom 302 revisited after delivery. Three-day dietary records were assessed at each visit. Blood was collected for thyroid function test. Obstetrical and birth outcomes were obtained.

RESULTS

The median dietary iodine intake was 459 μg/day (interquartile range [IQR] 326.5-647.4 μg/day) during pregnancy. Dietary iodine intake by quartile was not significantly associated with maternal thyroid status, or obstetrical or neonatal outcomes. However, the dietary iodine intake in the early postpartum period was 1759 μg/day (IQR 1026.7-2491.1 μg/day) because of a marked increase in seaweed soup consumption. Of all women, 25.8% consumed seaweed soup more than once over the 3 days of dietary records when pregnant, but the figure rose to 93.4% postpartum. Of postpartum women who consumed seaweed soup daily, the median dietary iodine intakes were 1355, 2394, and 3063 μg/day (soup at one, two, and three-or-four meals).

CONCLUSIONS

In these iodine-replete pregnant women, dietary iodine intake during pregnancy showed no effect on maternal thyroid function or birth outcomes. However, iodine intake in the early postpartum period was markedly increased by the frequency of seaweed soup consumption.

Exploring the Complementarity of Fortification and Dietary Diversification to Combat Micronutrient Deficiencies: A Scoping Review

Achieving a balanced and diverse diet remains a challenge for many people, contributing to an ongoing burden of micronutrient deficiencies, particularly in low-income settings. Fortification or dietary diversification are common food-based approaches. We conducted a scoping review to: 1) find evidence on whether combined food-based strategies are more effective than single strategies, and 2) understand how strategies implemented together could complement each other to achieve optimal nutritional impact on populations. Peer-reviewed articles selected (n = 21) included interventions or observational studies (n = 13) and reviews (n = 8). We found little evidence of an added nutritional impact. On the other hand, it is apparent that fortification and dietary diversification target different types of settings (urban compared with rural) and foods (that is, low priced compared with highly priced). Further research is needed to understand the complementarity of these approaches and establish evidence of the effectiveness of combined strategies to foster policy adoption.

Can Mild-to-Moderate Iodine Deficiency during Pregnancy Alter Thyroid Function? Lessons from a Mother-Newborn Cohort

Severe iodine deficiency during pregnancy has substantial hormonal consequences, such as fetal brain damage. Data on the potential effects of mild-to-moderate iodine deficiency on the thyroid function of pregnant women and their newborns are scarce and divergent. We investigated the association between iodine intake in pregnancy and maternal and neonatal thyroid function in a region with mild-to-moderate iodine deficiency. Pregnant women’s iodine status was evaluated using an iodine food frequency questionnaire, serum thyroglobulin (Tg), and urinary iodine concentration (UIC). Neonatal thyrotropin (nTSH) values were measured after birth. Obstetrics and anthropometric data were also collected. Among the 178 women (median age 31 years) included in the study, median (interquartile range) estimated dietary iodine intake, Tg and UIC were 179 (94−268) μg/day, 18 (11−33) μg/L, and 60 (41−95) μg/L, respectively. There was a significant inverse association of iodine intake with Tg values among the study population (β = −0.2, F = 7.5, p < 0.01). Women with high free triiodothyronine (FT3) values were more likely to exhibit an estimated iodine intake below the estimated average requirement (160 μg/day, odds ratio [OR] = 2.6; 95% confidence interval [CI], 1.1−6.4; p = 0.04) and less likely to consume iodine-containing supplements (OR = 0.3, 95% CI, 0.1−0.8; p = 0.01). It is possible that thyroid function may be affected by iodine insufficiency during pregnancy in regions with mild-to-moderate iodine deficiency. The relatively small sample size of the studied population warrants further investigation.

Schmidt R, N. Pearce E. Prenatal Exposure to Per- and Polyfluoroalkyl Substances, Maternal Thyroid Dysfunction, and Child Autism Spectrum Disorder

Autism spectrum disorder (ASD), with its high economic and societal costs, is a growing public health concern whose prevalence has risen steadily over the last two decades. Although actual increased incidence versus improved diagnosis remains controversial, the increased prevalence of ASD suggests non-inherited factors as likely contributors. There is increasing epidemiologic evidence that abnormal maternal thyroid function during pregnancy is associated with increased risk of child ASD and other neurodevelopmental disorders. Prenatal exposure to endocrine-disrupting chemicals such as per- and polyfluoroalkyl substances (PFAS) is known to disrupt thyroid function and can affect early brain development; thus, thyroid dysfunction is hypothesized to mediate this relationship. The concept of a potential pathway from prenatal PFAS exposure through thyroid dysfunction to ASD etiology is not new; however, the extant literature on this topic is scant. The aim of this review is to evaluate and summarize reports with regard to potential mechanisms in this pathway.

Iodine status, household salt iodine content, knowledge and practice assessment among pregnant women in Butajira, South Central Ethiopia

BACKGROUND

Iodine is one of the crucial micronutrients needed by the human body, and is vitally important during pregnancy. This study aimed to determine the relationship between the iodine status of pregnant women and their knowledge, and practices regarding iodized salt. All participants were enrolled in the Butajira nutrition, mental health and pregnancy (BUNMAP) cohort, Butajira, Ethiopia in February-May, 2019.

METHODS

In this cross-sectional study, 152 pregnant women without hypertension or known thyroid disease before or during pregnancy were randomly selected from the BUNMAP mother to child cohort (n = 832). Spot urine samples were collected to estimate the level of urinary iodine concentration (UIC). Salt samples were also collected from their homes. The Sandall-Kolthoff (S-K) method was used to measure the level of iodine in the urine samples, and iodometric titration was used to measure the level of iodine in the salt. Data was entered and cleaned using Epi-info version 3.5.3 and then exported to SPSS version 20 for further analysis. Multivariate logistic regression analysis was performed to identify associations in the collected data.

RESULTS

The WHO recommended level of iodine for populations of pregnant women is 150-249 F06Dg/L. The median UIC among pregnant women in this study was 151.2 μg/L [interquartile range (IQR) = 85.5-236.2 F06Dg/L], at the low end of this range. About half (49.65%) of the participants were likely to be iodine deficient. There was a significant association between having a formal job (AOR = 2.56; CI = 1.11-5.96) and iodine sufficiency. Based on a cutoff of >15 ppm (mg/kg), 91.7% (95% CI: 87.2-96.2) of the salts collected from the household had adequate iodine content. The median iodine level of the collected salt samples was 34.9 mg/kg (ppm) (IQR = 24.2-44.6 mg/kg).

CONCLUSIONS

The UNICEF 2018 guidelines for adequate iodine nutrition in pregnant women include both a recommended median range of 150-249 μg/L, and an upper limit of 20% on the fraction of the population with UIC below 50 μg/L. Because our study population's median level is 151.2 μg/L and the percentage of pregnant women with urinary iodine concentration of less than 50 μg/L is 9.7% (14/145), the women received adequate iodine nutrition. The availability of adequately iodized salt in households is more than 90%, as recommended by WHO. In light of previous iodine deficiency in this region of Ethiopia, the salt iodization program promotes the health of babies and mothers.

The role of nutrients in human neurodevelopment and their potential to prevent neurodevelopmental adversity

Nutritional deficits or excesses affect a huge proportion of pregnant women worldwide. Maternal nutrition has a significant influence on the fetal environment and can dramatically impact fetal brain development. This paper reviews current nutritional supplements that can be used to optimise fetal neurodevelopment and prevent neurodevelopmental morbidities, including folate, iodine, vitamin B12, iron, and vitamin D. Interestingly, while correcting nutritional deficits can prevent neurodevelopmental adversity, overcorrecting them can in some cases be detrimental, so care needs to be taken when recommending supplementation in pregnancy. The potential benefits of using nutrition to prevent neurodiversity is shown by promising nutraceuticals, sulforaphane and creatine, both currently under investigation. They have the potential to promote improved neurodevelopmental outcomes through mitigation of pathological processes, including hypoxia, inflammation, and oxidative stress. Neurodevelopment is a complex process and whilst the role of micronutrients and macronutrients on the developing fetal brain is not completely understood, this review highlights the key findings thus far.

Recent Advances in Biosensor Technologies for Point-of-Care Urinalysis

Human urine samples are non-invasive, readily available, and contain several components that can provide useful indicators of the health status of patients. Hence, urine is a desirable and important template to aid in the diagnosis of common clinical conditions. Conventional methods such as dipstick tests, urine culture, and urine microscopy are commonly used for urinalysis. Among them, the dipstick test is undoubtedly the most popular owing to its ease of use, low cost, and quick response. Despite these advantages, the dipstick test has limitations in terms of sensitivity, selectivity, reusability, and quantitative evaluation of diseases. Various biosensor technologies give it the potential for being developed into point-of-care (POC) applications by overcoming these limitations of the dipstick test. Here, we present a review of the biosensor technologies available to identify urine-based biomarkers that are typically detected by the dipstick test and discuss the present limitations and challenges that future development for their translation into POC applications for urinalysis.

Effects of maternal iodine nutritional status on neurodevelopmental and cognitive function of rat offspring

Objectives

This study aimed to explore the effect of maternal iodine status on the brain development of offspring in rats. Since in human studies, the interference of environmental factors and other nutrients cannot be removed.

Materials and methods

A total of 48 female Wistar rats were randomly divided into four groups: low iodine (LI), normal iodine (NI), 10-fold high iodine (10HI), and 50-fold high iodine (50HI). The rats were killed on the 15th day of pregnancy and lactation after collecting 24-h urine. The iodine concentration in 24-h urine, blood, and placenta of pregnant rats, and 24-h urine, milk, blood, and mammary glands of lactating rats was determined by inductively coupled plasma mass spectrometry. The thyroid hormone of pregnant and lactating rats was detected by chemiluminescence. The offspring were subjected to the Morris water maze on the 10th day after birth. Serum was collected to detect the thyroid hormone of offspring. The protein expression of neuroendocrine-specific protein (NSP)-A and brain-derived neurotrophic factor (BDNF) in the offspring brain were studied.

Results

Iodine storage in the placenta during pregnancy and mammary glands during lactation was positively correlated with iodine intake, and iodine storage in the placenta and mammary glands in the 50HI group was significantly higher than that in the NI group (P = 0.045 and P = 0.040). Compared with the NI group, the offspring thyroid-stimulating hormone (TSH) level was significantly higher in the 10HI group (P = 0.046), and the FT4 level was significantly lower in the 50HI group (P = 0.032). The Morris water maze showed that LI and 50HI groups required longer time and distance to find the platform than the NI group (P &lt; 0.001). The platform crossing numbers in the LI and 50HI groups decreased significantly (P &lt; 0.001). The expression of NSP-A in offspring brain was lower in the 10HI and 50HI groups than in the NI group (P = 0.026 and P = 0,008). BDNF expression levels were significantly lower in the LI, 10HI, and 50HI groups than in the NI group (P &lt; 0.001).

Conclusion

Maternal iodine intake affects iodine storage in the placenta and lactating mammary gland, which in turn affects thyroid function and BDNF and NSP-A expression in the offspring.

Study on the Effect of Different Iodine Intake on Hippocampal Metabolism in Offspring Rats

Iodine is an essential trace element in the human body. Severe maternal iodine deficiency during pregnancy leads to obvious intellectual disability in the offspring. The effects of iodine deficiency on brain development have been demonstrated, but there is no clear evidence of the effects of iodine excess on brain development. To clarify the effects of iodine excess on the brain development of offspring and to provide clues to the mechanisms underlying the effects of iodine deficiency and iodine excess on the brain development of offspring. In this study, animal models with different iodine intakes were constructed using potassium iodate (KIO₃). The models included four experimental groups (low-iodine group one (LI, 0μg/L iodine), low-iodine group two (LII, 5μg/L iodine), high-iodine group one (HI, 3000μg/L iodine), and high-iodine group two (HII, 10000μg/L iodine)) and one control group (NI, 100μg/L iodine). There were 20 female rats in each group, and 8 offspring were chosen from each group following birth to assess metabolic alterations. The metabolites of subsets of brain hippocampal tissue were profiled by ultra-performance liquid chromatography-linked electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOFMS) and the results were subjected to multivariate data analysis. Differential substances were screened by t test (p<0.05), principal component analysis (PCA), and partial least squares analysis (PLS-DA, VIP>1). The thyroid function of the female rats in the experimental group was abnormally changed. Metabolic analysis showed that the five groups were separated which revealed significant differences in hippocampal tissue metabolism among the five groups of offspring. A total of 12 potential metabolites were identified, with the majority of them being related to amino acid and energy metabolism. These metabolites are involved in various metabolic pathways, are interrelated, and may play a function in brain development. Our study highlights changes in metabolites and metabolic pathways in the brain hippocampus of offspring rats with different iodine intakes compared to controls, revealing new insights into hippocampal metabolism in offspring rats and new relevant targets.

Noncompliance to iodine supplementation recommendation is a risk factor for iodine insufficiency in Portuguese pregnant women: results from the IoMum cohort

PURPOSE

After a recommendation for iodine supplementation in pregnancy has been issued in 2013 in Portugal, there were no studies covering iodine status in pregnancy in the country. The aim of this study was to assess iodine status in pregnant women in Porto region and its association with iodine supplementation.

METHODS

A cross-sectional study was conducted at Centro Hospitalar Universitário São João, Porto, from April 2018 to April 2019. Pregnant women attending the 1st trimester ultrasound scan were invited to participate. Exclusion criteria were levothyroxine use, gestational age < 10 and ≥ 14 weeks, non-evolutive pregnancy at recruitment and non-signing of informed consent. Urinary iodine concentration (UIC) was measured in random spot urine by inductively coupled plasma-mass spectrometry.

RESULTS

Median UIC was 104 μg/L (IQR 62-189) in the overall population (n = 481) of which 19% had UIC < 50 µg/L. Forty three percent (n = 206) were not taking an iodine-containing supplement (ICS) and median UIC values were 146 µg/L (IQR 81-260) and 74 µg/L (IQR 42-113) in ICS users and non-users, respectively (p < 0.001). Not using an ICS was an independent risk factor for iodine insufficiency [adjusted OR (95% CI) = 6.00 (2.74, 13.16); p < 0.001]. Iodised salt use was associated with increased median iodine-to-creatinine ratio (p < 0.014).

CONCLUSIONS

A low compliance to iodine supplementation recommendation in pregnancy accounted for a mild-to-moderately iodine deficiency. Our results evidence the need to support iodine supplementation among pregnant women in countries with low household coverage of iodised salt. Trial registration number NCT04010708, registered on the 8th July 2019.

Incidence tendency, etiological classification and outcome of congenital hypothyroidism in Guangzhou, China: an 11-year retrospective population-based study

OBJECTIVES

An increased incidence of congenital hypothyroidism (CH) has been described worldwide over the years. In this study, we aimed to investigate the epidemiologic characteristics of CH, the iodine status in Guangzhou, China and to investigate which factors might influence the CH incidence during the period 2010-2020.

METHODS

We retrospectively reviewed all cases of CH detected by newborn screening during the period 2010-2020. CH was classified as either suspected thyroid dyshormonogenesis (SDH) or thyroid dysgenesis (TD) based on thyroid ultrasound at first diagnosis. Patients were re-evaluated after 4 weeks of L-thyroxine withdrawal at age of 2-3 years to confirm the diagnosis of permanent CH (PCH) or transient CH (TCH).

RESULTS

From 2010 to 2020, 1,655 patients with CH were confirmed from 2,400,383 newborns (1:1,450). The CH incidence increased from 1:2,584 in period [2010-2014] to 1:1,086 in period [2015-2020]. Among the 1,337 patients with thyroid ultrasound, 84.29% were SDH whereas 15.71% had TD. Further analysis revealed that more SDH (78.32%) were TCH whereas more TD (87.12%) turned to be PCH. The proportion of blood spot thyrotropin values >5 mIU/L ranged from 8.03 to 20.46%, indicating iodine deficiency. The prevalence of preterm infants increased from 5.50% in period [2010-2014] to 7.06% in period [2015-2020] (p<0.001).

CONCLUSIONS

In the past decade, the CH incidence has increased progressively. SDH was the majority of CH, most of which were TCH, while most patients with TD were PCH. The increased incidence might be mainly due to iodine deficiency and increased rates of preterm infants in our study.