Maternal iodine status and the thyroid function of pregnant mothers and their neonates in Jaffna District of Sri Lanka

Maternal Iodine Status and Birth Outcomes: A Systematic Literature Review and Meta-Analysis

Background & aims: Iodine is important for thyroid function during pregnancy to support fetal growth, but studies of maternal iodine status and birth outcomes are conflicting. We aimed to quantify the association between iodine status and birth outcomes, including potential threshold effects using nonlinear dose−response curves. Methods: We systematically searched Medline and Embase to 10 October 2022 for relevant cohort studies. We conducted random-effects meta-analyses of urinary iodine concentration (UIC), iodine:creatinine ratio (I:Cr), and iodide intake for associations with birth weight, birth weight centile, small for gestational age (SGA), preterm delivery, and other birth outcomes. Study quality was assessed using the Newcastle-Ottawa scale. Results: Meta-analyses were conducted on 23 cohorts with 42269 participants. Birth weight was similar between UIC ≥ 150 μg/L and <150 μg/L (difference = 30 g, 95% CI −22 to 83, p = 0.3, n = 13, I2 = 89%) with no evidence of linear trend (4 g per 50 μg/L, −3 to 10, p = 0.2, n = 12, I2 = 80%). I:Cr was similar, but with nonlinear trend suggesting I:Cr up to 200 μg/g associated with increasing birthweight (p = 0.02, n = 5). Birthweight was 2.0 centiles (0.3 to 3.7, p = 0.02, n = 4, I2 = 0%) higher with UIC ≥ 150 μg/g, but not for I:Cr. UIC ≥ 150 μg/L was associated with lower risk of SGA (RR = 0.85, 0.75 to 0.96, p = 0.01, n = 13, I2 = 0%), but not with I:Cr. Conclusions: The main risk of bias was adjustment for confounding, with variation in urine sample collection and exposure definition. There were modest-sized associations between some measures of iodine status, birth weight, birth weight centile, and SGA. In pregnancy, we recommend that future studies report standardised measures of birth weight that take account of gestational age, such as birth weight centile and SGA. Whilst associations were modest-sized, we recommend maintaining iodine sufficiency in the population, especially for women of childbearing age on restricted diets low in iodide.

Factors influencing the iodine status of children aged 12 to 59 months from Jaffna District, Sri Lanka in the post-iodization era; a descriptive, cross-sectional study

BACKGROUND

Iodine status, including Iodine Deficiency (ID) of the children aged 12-59 months of Jaffna District, Sri Lanka, have never been studied. This study thus aimed to assess ID among children aged 12-59 months by monitoring the Urinary Iodine Concentrations (UIC), the prevalence of goitre, and the factors causing ID.

METHOD

A cross-sectional study was conducted among 846 children aged 12-59 months in Jaffna District, Sri Lanka. Sociodemographic characteristics and other factors were collected using an interviewer-administered questionnaire. Dietary pattern of children was obtained using semi-quantitative food frequency questionnaire. We performed urinary iodine estimation and physical examinations to detect the goitre, according to the World Health Organization criteria. A multivariate logistic linear regression model was used to identify the factors that causing ID.

RESULT

The median UIC was 146.4 μg/L (interquartile range = 112.6-185.3 μg/L). Based on the UIC (<100 μg/L), 17.8% had ID, of which 15.7% and 2.1% had mild and moderate ID. The mean consumption of iodine from food was 128.7 (±20.2) μg/day. Gender variation had no influence on ID (p>0.05). Median UIC was significantly associated with living area, wealth status, type of drinking water, and method of iodized salt usage. A higher percentage of ID was significantly associated with younger age [AOR 2.32 (95% CI: 1.31-4.10)], urban area [AOR 1.94 (95% CI 1.27-2.96)], inland regions [AOR 3.20 (95% CI 1.85-5.55)], improper method of iodized salt usage [AOR 3.63 (95% CI: 1.38-9.56)], and low consumption of iodine-containing foods. The neck palpation revealed that only three children had goitre (0.4%).

CONCLUSION

This study revealed that high ID among the children in Jaffna children was due to improper usage of iodized salt, even though the iodized salt is freely available in the region, living area, and age, while the prevalence of goitre was not significantly identified as a public health problem.

The association between COVID-19 pandemic and maternal isolated hypothyroxinemia in first and second trimesters

BACKGROUND

The outbreak of COVID-19 epidemic has induced entire cities in China placed under 'mass quarantine'. The majority of pregnant women have to be confined at home may be more vulnerable to stressors. In our study, we aimed to explore the effects of the epidemic on maternal thyroid function, so as to provide evidence for prevention and intervention of sustained maternal and offspring's health impairment produced by thyroid dysfunction.

METHODS

The subjects were selected from an ongoing prospective cohort study. we included the pregnant women who receive a thyroid function test during the COVID-19 epidemic and those receiving the test during the corresponding lunar period of 2019. A total of 7148 pregnant women with complete information were included in the final analysis. Multivariate linear and logistic regression models were used for analyzing the association of COVID-19 pandemic with FT4 levels and isolated hypothyroxinemia.

RESULTS

We found a decreased maternal FT4 level during the period of the COVID-19 pandemic in first and second trimesters (β = -0. 131, 95%CI = -0.257,-0.006，p = 0.040) and in first trimester (β = -0. 0.176, 95%CI = -0.326,-0.026，p = 0.022) when adjusting for 25 (OH) vitamin D, vitamin B12, folate and ferritin and gestational days, maternal socio-demographic characteristics and health conditions. The status of pandemic increased the risks of isolated hypothyroxinemia in first and second trimesters (OR = 1.547, 95%CI = 1.251,1.913, p < 0.001) and first trimester (OR = 1.651, 95%CI = 1.289,2.114, p < 0.001) when adjusting for the covariates. However, these associations disappeared in the women with positive TPOAb (p > 0.05). Additionally, we found associations between daily reported new case of COVID-19 and maternal FT4 for single-day lag1, lag3 and multi-day lag01 and lag04 when adjusting for the covariates (each p < 0.05).

CONCLUSIONS

Mass confinement as a primary community control strategy may have a significant cost to public health resources. Access to health service systems and adequate medical resources should be improved for pregnant women during the COVID-19 pandemic.

Do maternal urinary iodine concentration or thyroid hormones within the normal range during pregnancy affect growth parameters at birth? A systematic review and meta-analysis

CONTEXT

Iodine, an essential constituent of thyroid hormones, is required for proper growth and development.

OBJECTIVE

To investigate whether growth parameters at birth are associated with maternal urinary iodine concentration (UIC) or normal ranges of thyroid hormones during pregnancy.

DATA SOURCES

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, electronic databases (namely, MEDLINE, Web of Science, the Cochrane Library, Scopus, and Google Scholar) were searched between January 1988 and November 2018 to identify relevant articles.

DATA EXTRACTION

Data from the studies included were independently extracted by 2 investigators using standardized forms developed for this review.

DATA ANALYSIS

The pooled mean birth weight, length, and head circumference values, and 95% confidence intervals were estimated in newborns born to women with UIC < 150 and UIC ≥150 μg/L during pregnancy. Possible linear or nonlinear associations between maternal UIC and the aforementioned anthropometric measures were evaluated. A narrative synthesis of the data was performed for thyroid hormones with levels within the normal range.

RESULTS

Of the 123 studies identified, 11 were eligible for inclusion in the meta-analysis. The pooled mean birth weight, length, and head circumference in newborns whose mothers had UIC < 150 μg/L vs UIC ≥150 μg/L were 2898 g vs 2900 g (P = 0.970), 49.6 cm vs 49.4 cm (P = 0.880), and 34.0 cm vs 34.1 cm (P = 0.933), respectively. Dose-response meta-analyses revealed no significant linear or nonlinear associations between maternal UIC during pregnancy and anthropometric measures at birth. Among the different thyroid function parameters evaluated, high-normal values of maternal free thyroxine and thyrotropin during pregnancy were inversely associated with neonatal birth weight.

CONCLUSION

This systematic review showed that birth weight may be affected by even mild variations in the normal concentrations of maternal thyroid hormones. However, in the current meta-analysis, birth anthropometric measures were not associated with maternal UIC during pregnancy.

Thyroglobulin Concentration and Maternal Iodine Status During Pregnancy: A Systematic Review and Meta-Analysis

Background: Literature to date has been inconclusive regarding the value of thyroglobulin (Tg) as a marker of iodine status in pregnant women. This systematic review and meta-analysis is one of the first to assess whether Tg concentration accurately reflects iodine status among pregnant women. Methods: We searched MEDLINE, the Web of Science, the Cochrane Library, Scopus, and other relevant databases to identify relevant studies published in the English language, between January 1988 and December 2018. The criteria for study inclusion in the systematic review were human studies, healthy pregnant women as participants, and available data for maternal urinary iodine concentration (UIC) and Tg level. Each study was assessed for quality and risk of bias. The pooled mean Tg values, and 95% confidence intervals were estimated in a population of women with UIC <150 and UIC ≥150 μg/L during pregnancy. Potential linear or nonlinear dose-response associations between maternal UIC and Tg concentration were examined. Results: Of 814 identified studies, 25 were eligible for inclusion in the meta-analysis. Studies included were conducted in Africa, Asia, Europe, South America, and the Oceania. The pooled mean (95% confidence interval [CI]) Tg concentration in iodine-deficient pregnant women was higher than that in iodine-sufficient pregnant women (10.73 μg/L [5.65-15.82] vs. 7.34 μg/L [2.20-12.47]); a comparison of the 95% CI showed that none of these values was significantly different. No significant differences were observed in Tg concentration between the two groups in each trimester of pregnancy. Dose-response meta-analyses revealed a significant nonlinear association between maternal UIC and Tg concentration during pregnancy. Among populations of pregnant women, an inverse association was found between UIC values <100 μg/L and Tg concentration (p-linearity = 0.007; p-nonlinearity = 0.027); however, higher values of UIC were not associated with Tg concentration. Conclusions: Our meta-analysis showed that Tg concentration can be a sensitive indicator of iodine deficiency, specifically in populations of pregnant women with median UIC <100 μg/L. Further studies are warranted to determine the sensitivity of Tg at different degrees of iodine deficiency during pregnancy.

Non-iodized salt consumption among women of reproductive age in sub-Saharan Africa: a population-based study

OBJECTIVE

To identify countries in sub-Saharan Africa (SSA) that have not yet achieved at least 90 % universal salt iodization and factors associated with the consumption of non-iodized salt among women of reproductive age.

DESIGN

A cross-sectional study using data from Demographic and Health Surveys (DHS). The presence of iodine in household salt (iodized or non-iodized), which was tested during the survey process, was the study outcome. Multivariable logistic regression models were used to determine independent factors associated with the consumption of non-iodized salt among women of reproductive age.

SETTING

There were eleven countries in SSA that participated in the DHS since 2015 and measured the presence of iodine in household salt.

PARTICIPANTS

Women (n 108 318) aged 15-49 years.

RESULTS

Countries with the highest rate of non-iodized salt were Senegal (29·5 %) followed by Tanzania (21·3 %), Ethiopia (14·0 %), Malawi (11·6 %) and Angola (10·8 %). The rate of non-iodized salt was less than 1 % in Rwanda (0·3 %), Uganda (0·5 %) and Burundi (0·8 %). Stepwise multivariable logistic regression showed that women were more likely to be using non-iodized salt (adjusted OR; 95 % CI) if they were poor (1·62; 1·48, 1·78), pregnant (1·16; 1·04, 1·29), aged 15-24 years (v. older: 1·14; 1·04, 1·24) and were not literate (1·14; 1·06, 1·23).

CONCLUSIONS

The use of non-iodized salt varies among SSA countries. The higher level of use of non-iodized salt among poor, young women and pregnant women is particularly concerning.

Effect of maternal and neonatal factors on neonatal thyroid stimulating hormone: Results from a population-based prospective cohort study in China

OBJECTIVE

Neonatal TSH screening is effective in detecting congenital hypothyroidism and estimating iodine status in a given population, but various factors influence TSH levels. The aim of this study was to evaluate the effect of maternal and neonatal factors on neonatal TSH levels.

DESIGN AND SETTING

Data were obtained from an ongoing prospective cohort study. A total of 988 pregnant women and their newborn infants participated in the study from April 2015 to May 2017 at Tianjin Maternal and Child Health Center and Tanggu Maternity Hospital in Tianjin, China. Maternal demographic information, including age, height, and parity, was recorded by questionnaire. Fasting blood and urinary samples were collected from all pregnant women. After parturition, information on gestation duration, mode of delivery, neonatal sex, neonatal TSH, neonatal birth weight, and neonatal birth height were recorded.

RESULTS

Maternal age, maternal BMI, gestation duration, parity, and neonatal birth weight and height were significantly correlated with neonatal TSH (p < 0.05). Quantile regression revealed that maternal age, TSH, FT₄, and gestation duration were positively correlated with neonatal TSH level. A logistic regression model identified maternal BMI, TSH, and birth height as risk factors for having neonatal TSH > 5 mIU/L (p < 0.05).

CONCLUSION

Neonatal TSH levels are dynamic and may be affected by several maternal and neonatal factors including maternal age, TSH, FT₄, and birth weight and height. Identification of these confounders is useful for assessing the status of neonatal thyroid development. STRENGTHS AND LIMITATIONS OF THIS STUDY: (1) Iodine deficiency disorder has generally been eliminated, so the median urinary iodine concentration of pregnancy is higher than 150 μg/L even in mildly or moderately iodine deficient areas. (2) Unlike many other studies, which did not consider the complexity of factors or examined only one or two variables, this study used a multivariate model to analyze the data. (3) This study examined numerous high-risk factors in pregnant women and considered the biological interrelation between them. Future studies should consider these confounding factors for neonatal TSH levels and establish a proper neonatal TSH range for monitoring the iodine status of a population or diagnosing congenital hypothyroidism.

Socio-economic and spatial correlates of subclinical iodine deficiency among pregnant women age 15-49 years in Tanzania

BACKGROUND

Iodine deficiency is a widespread global health problem that affects about 2 billion people each year. Pregnant women are particularly vulnerable to iodine deficiency due to increased iodine requirement leading to death, miscarriage, and stillbirth. Iodine deficiency also has significant negative effects on newborns including impaired cognitive development, impaired learning capabilities, and stunting. This study looks at the association between subclinical iodine deficiency and demographic factors including age, wealth index, education, family size, geographical zone, number of children, fish consumption, pregnancy trimester and household salt in pregnant women aged 15-49 years in Tanzania.

METHODS

The 2010 Tanzania Demographic and Health Survey (TDHS) data was re analysed. Subclinical iodine deficiency is classified as a urinary iodine concentration (UIC) of <150 μg/L.

RESULTS

Results showed that the prevalence of iodine deficiency (54%) was unacceptably high among pregnant women. The results of multiple logistic regression model found that number of children, wealth index, household salt, and geographical zone were significantly associated with iodine deficiency in these women.

CONCLUSION

These results indicate a need to implement interventions to increase iodine intake that targets pregnant women with the specific demographic characteristics.

Maternal marginal iodine deficiency limits dendritic growth of cerebellar purkinje cells in rat offspring by NF-κB signaling and MAP1B

Iodine deficiency (ID) during early pregnancy had an adverse effect on children's psychomotor and motor function. It is worth noting that maternal marginal ID tends to be a common public health problem. Whether marginal ID potentially had adverse effects on the development of cerebellum and the underlying mechanisms remain unclear. Therefore, our aim was to study the effects of marginal ID on the dendritic growth in filial cerebellar Purkinje cells (PCs) and the underlying mechanism. In the present study, we established Wistar rat models by feeding dam rats with a diet deficient in iodine and deionized water supplemented with potassium iodide. We examined the total dendritic length using immunofluorescence, and Western blot analysis was conducted to investigate the activity of nuclear factor-κB (NF-κB) signaling and microtubule-associated protein 1B (MAP1B). Our results showed that marginal ID reduced the total dendritic length of cerebellar PCs, slightly down-regulated the activity of NF-κB signaling and decreased MAP1B in cerebellar PCs on postnatal day (PN) 7, PN14, and PN21. Our study may support the hypothesis that decreased T₄ induced by marginal ID limits PCs dendritic growth, which may involve in the disturbance of NF-κB signaling and MAP1B on the cerebellum. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1241-1251, 2017.