Prevalence of insufficient iodine intake in pregnancy worldwide: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Iodine deficiency in pregnant women is related to impaired foetal growth and development. The objective of this study was to estimate the prevalence of insufficient iodine intake in pregnant women from different regions of the world.

SUBJECTS/METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, five electronic databases and Google Scholar grey literature were searched until 10 April 2021. Two reviewers independently conducted article selection, data extraction, and assessment of the risk of bias. Meta-analyses with random effects, subgroup analyses, and meta-regressions were performed.

RESULTS

In total, 4639 observational articles were found, with 61 eligible for inclusion. The population consisted of 163,021 pregnant women adults and adolescents, and the overall prevalence of insufficient iodine intake was 53% (95% confidence interval [CI]: 47-60; I² = 99.8%). Pregnant women who live in insufficient iodine status country had a higher prevalence (86%; 95% CI: 78-93; I² =97.0%) of inadequate iodine nutritional status than to those living in country considered sufficient (51%; 95% IC: 45-57; I² = 99.8%).

CONCLUSION

Despite the progress in iodine fortification policies and periodic monitoring of the iodine nutritional status of the population worldwide, salt iodination alone may not be sufficient to provide adequate iodine status to pregnant women. Thus, other actions may be necessary to improve the nutritional clinical care of pregnant group.

Household Iodized Salt, Iodine Intake, and Thyroid Dysfunction in Reproductive Age Women in Different Regions of Iodine Adequacy

Iodine deficiency affects people of all age groups and yields detrimental health effects known as Iodine Deficiency Disorders (IDD). Universal Salt Iodization (USI) where above 90% household use iodized salt became the main program to optimized population iodine status. This study aimed to analyze iodine in salt, iodine status and thyroid functions from three different IDD endemic regions.

METHODS

This was a cross-sectional study, with women of reproductive age (15 to 45 y old) as subjects, conducted in plain area (Yogyakarta) city (n=250), mountainous area (Bukit Tinggi city) (n=249), and combination of mountaneous and plain area (Purworejo regency) (n=249). Urinary iodine (UIE), prevalence of hyperthyroidism, and hypothyroidism (diagnostic based on combination of TSH and fT4 level), also the presence or absence and level of iodine in salt were assessed.

RESULT

Iodized salt coverage have reached >90% household in all three region, while titration found 75.6% with adequate level of iodine in salt (>30 ppm), with wide range of iodine level in salt (0.00-218.2 ppm). With that condition, population in plain and combination of plain and mountainous area have more than adequate iodine status (218 μg/L and 224 μg/L), while population in mountaneous area still in mild iodine deficiency status (UIE median of 88 μg/L). Most population is in euthyroid condition. Hyperthyroidism, subclinical hyperthyroidism, secondary hyperthyroidism, subclinical hypothyroidism, and hypothyroidism were found in 0.7%, 4.8%, 0.4%, 8.9%, and 0.9% population consecutively. There were no relationship between iodine status and prevalence of hyperthyroidism and hypothyroidism, but subclinical hypothyroidism most prevalent in excess UIE population (12.5% vs 8.3%).

CONCLUSION

All three regions have achieved USI target. But the risk of iodine deficiency still found in mountaneous area. Household iodized salt coverage discrepancy between rapid test and titration strengthen the need of more accurate but efficient test of iodine level in salt.

Serum Selenium Status and Its Interrelationship with Serum Biomarkers of Thyroid Function and Antioxidant Defense in Hashimoto's Thyroiditis

Selenium (Se) deficiency has been implicated in the pathogenesis of Hashimoto’s thyroiditis (HT), although the available evidence is limited. The present study aimed to explore the interrelationships between serum Se status with measures of thyroid function and antioxidant defense in new cases of HT patients with hypoechogenic thyroid. HT patients (n = 49) and matched controls (n = 50) were recruited. Selenium, thyroid hormone panel, thyroid volume (TVol), glutathione (GSH), glutathione peroxidase3 (GPx3) activity, urinary iodine concentration (UIC), and urinary creatinine (Cr) were assessed. HT patients exhibited lower Se levels compared to controls (p < 0.001) with the rates of Se-deficient (<0.85 µmol/L) participants being 58.8% and 34%, respectively. Se-deficient patients exhibited higher thyroid stimulating hormone (TSH), Thyroid volume (TVol), thyroglobulin, antibody-titers, GPx3 activity and UIC/Cr compared to Se-sufficient patients (all p < 0.001). In the Se-deficient patients, inverse correlations were seen between Se-levels with TSH, TVol, and Thyroid peroxidase antibody (TPO-Ab) (all p < 0.001). This study is the first to uncover that coexisting Se-deficiency and elevated iodine in HT may enhance autoimmune reactions and accelerate the deterioration of thyroid function through oxidative stress. Our study also highlights the importance of optimal Se status in this disease, thus providing a rationale for the execution of intervention trials for the evaluation of the clinical benefits of antioxidant-status improvement in HT.

[Factors associated with the nutritional status of iodine in the maternal-infant group: a systematic review]

This article sets out to identify the socio-demographic and nutritional factors associated with the nutritional status of iodine in the maternal-infant group. The review was based on the Prisma method and the Medline (PubMed), Scopus and Lilacs databases were consulted. The search was conducted in December 2018, using the key words nutritional status, iodine, infant, pregnant and lactating. The selection followed the stages of excluding duplicated articles, reading the titles, abstracts and texts in full. A total of 1,500 studies were identified and 26 met the inclusion criteria. The methodological quality of the studies was evaluated using the questionnaire proposed by Downs and Black. There was an association between the sociodemographic factors of income, education, maternal and gestational age, uniformity and place of residence in rural or urban areas with the nutritional state of iodine. In relation to dietary factors, the consumption of supplements, iodized salt and dietary sources of iodine, especially dairy products, play a protective role to avoid the deficiency. It is necessary to create more specific and effective strategies that address all the factors that affect the nutritional state of iodine to avoid the disorders resulting from the deficiency.