The Impact of Iodine Status on the Recall Rate of the Screening Program for Congenital Hypothyroidism: Findings from Two National Studies in Iran

Physical Development at School Entry in Children with Congenital Hypothyroidism Diagnosed by the National Program of Newborn Screening in Iran

BACKGROUND

The newborn screening program for diagnosing and treating children with congenital hypothyroidism (CH) in Iran was established in 2004.

OBJECTIVES

This study aimed to evaluate the national program's success in maintaining the physical development and anthropometric indexes of children with CH.

METHODS

This historical cohort study was carried out in five provinces located in five different geographical regions of Iran. The anthropometric indexes, including weight, height, and head circumference of 240 children diagnosed with transient congenital hypothyroidism (TCH) (n = 131) and permanent congenital hypothyroidism (PCH) (n = 109) were measured and compared with those of 240 healthy children aged six.

RESULTS

Mean ± standard deviation (SD) of weight, height, and head circumference of children with CH aged six were 20304.8 ± 4457.9 g, 115.6 ± 5.9 cm, and 50.8 ± 1.7 cm, respectively. Mean ± SD of height (116.7 ± 6.1 cm) and head circumference (51.1 ± 1.7 cm) in the control (healthy) group were significantly higher than those of the CH children group (P < 0.05). Mean ± SD weight in the control group (20741.2 ± 4337.3 g) was higher than that in the CH group (20304.8 ± 4457.9 g). However, the difference was not statistically significant (P = 0.3). No significant difference was observed between TCH and PCH children in the subgroup analysis (P > 0.05).

CONCLUSIONS

Although the mean of anthropometric indexes in CH patients was slightly lower than that in healthy children aged six, the difference between the two groups was insignificant. The physical development of children with CH was evaluated as good. Our results suggested that the newborn screening program for identifying and treating children with CH in Iran may have improved the growth outcomes.

CaMKIV mediates spine growth deficiency of hippocampal neurons by regulation of EGR3/BDNF signal axis in congenital hypothyroidism

Congenital hypothyroidism (CH) will cause cognitive impairment in the condition of delayed treatment. The hippocampus is one of the most affected tissues by CH, in which the functional structures of hippocampal neurons manifest deficiency due to aberrant expression of effector molecules. The Ca²⁺/Calmodulin-dependent protein kinase, CaMKIV, is downregulated in the hippocampal neurons, influencing the growth of dendritic spines in response to CH. However, the underlying mechanism is not fully elucidated. In the present study, the early growth response factor 3 (EGR3) was regulated by CaMKIV in the hippocampal neurons of CH rat pups, as was analyzed by transcriptome sequencing and in vitro cell experiments. EGR3 localized within hippocampal neurons in CA1, CA3, and dentate gyrus regions. Deficient EGR3 in the primary hippocampal neurons significantly reduced the density of dendritic spines by downregulating the expression of BDNF, and such effects could be rescued by supplementing recombinant BDNF protein. Taken together, CH mediates cognitive impairment of pups through the inactivation of CaMKIV in the hippocampal neurons, which decreases the expression of EGR3 and further reduces the production of BDNF, thereby impairing the growth of dendritic spines. Identifying CaMKIV/EGR3/BDNF pathway in the hippocampal neurons in the context of CH will benefit the drug development of intellectual disability caused by CH.

Geographic variations in the incidence of congenital hypothyroidism in China: a retrospective study based on 92 million newborns screened in 2013-2018

Background:

Although congenital hypothyroidism (CH) has been widely studied in Western countries, CH incidence at different administrative levels in China during the past decade remains unknown. This study aimed to update the incidence and revealed the spatial pattern of CH incidence in the mainland of China, which could be helpful in the planning and implementation of preventative measures.

Methods:

The data used in our study were derived from 245 newborns screening centers that cover 30 provinces of the Chinese Newborn Screening Information System. Spatial auto-correlation was analyzed by Global Moran I and Getis-Ord Gi statistics at the provincial level. Kriging interpolation methods were applied to estimate a further detailed spatial distribution of CH incidence at city level throughout the mainland of China, and Kulldorff space scanning statistical methods were used to identify the spatial clusters of CH cases at the city level.

Results:

A total of 91,921,334 neonates were screened from 2013 to 2018 and 42,861 cases of primary CH were identified, yielding an incidence of 4.66 per 10,000 newborns screened (95% confidence interval [CI]: 4.62–4.71). Neonates in central (risk ratio [RR] = 0.84, 95% CI: 0.82–0.85) and western districts (RR = 0.71, 95% CI: 0.69–0.73) had lower probability of CH cases compared with the eastern region. The CH incidence indicated a moderate positive global spatial autocorrelation (Global Moran I value = 0.394, P < 0.05), and the CH cases were significantly clustered in spatial distribution. A most likely city-cluster (log-likelihood ratio [LLR] = 588.82, RR = 2.36, P < 0.01) and 25 secondary city-clusters of high incidence were scanned. The incidence of each province and each city in the mainland of China was estimated by kriging interpolation, revealing the most affected province and city to be Zhejiang Province and Hangzhou city, respectively.

Conclusion:

This study offers an insight into the space clustering of CH incidence at provincial and city scales. Future work on environmental factors need to focus on the effects of CH occurrence.

Familial-Related Risks for Congenital Hypothyroidism in Iranian Newborns: A Population-Based Case-Control Study

BACKGROUND

Congenital hypothyroidism (CH), as one of the most common endocrine disorders, is a preventable cause of mental retardation.

OBJECTIVE

This study aimed to identify familial-related risk factors for CH in Iranian newborns.

METHODS

A population-based case-control study was performed on the National Registry System of patients with CH in Iran. In this study, 906 controls and 454 cases were studied for one year. Familial related factors were investigated using logistic regression models. Population attributable fraction (PAF) was also calculated for each significant risk factor.

RESULTS

Using multivariate analysis, an increased risk for CH was observed in patients with congenital anomalies (odds ratio (OR): 5.77, 95% confidence interval (CI): 2.37 - 14.01), history of mental retardation in family (OR:2.10, 95% CI: 1.15-3.83), mother's hypothyroidism during pregnancy (OR: 2.01, 95% CI: 1.33 - 3.03), intra-family marriage (OR:1.49, 95% CI: 1.18 - 1.89), gestational diabetes (OR: 1.69, 95% CI: 1.09 - 2.63), having a hypothyroid child in the family (OR: 2.48, 95% CI: 1.39 - 4.42), and twins or more (OR: 2.61, 95% CI: 1.31 - 5.21). The highest PAF among familial-related risk factors for CH is related to the intra-family marriage (14.9%).

CONCLUSIONS

This study revealed that familial-related risk factors and consanguine marriages play an essential role in the high incidence of CH in Iran. About 15% of CH in Iran could be attributed to intra-family marriage alone.

Investigating the incidence rate and geographical distribution of congenital hypothyroidism among neonates in Isfahan province using geographic information system (GIS) between 2002 and 2015

Background Congenital hypothyroidism (CH) is one of the main causes of mental retardation in neonates. The disease is associated with genetic, climatic and environmental factors. Accordingly, the present study was conducted to determine the incidence rate and correlation of geographic factors with CH in Isfahan province in order to explain the role of climatic factors in the incidence of disease in this province. Methods This cross-sectional study was conducted to determine the incidence rate and geographical distribution of CH in neonates born in the Isfahan province from the beginning of 2002 to the end of 2015. To estimate the geographic distribution, the ArcGIS software (version 10.3) was used and to investigate the relationship between geographical factors and CH, the Poisson regression test and dispersion diagrams were used. Data analysis was done using the SPSS16 software. Results According to the results of the screening of 1,006,404 neonates born in Isfahan, the mean incidence rate of CH in all infants was 2.3, and that in male and female infants was 2.39 and 2.2 per 1000 live births, respectively. There was a statistically significant correlation between the city of residence (p = 0.01), climatic conditions (p = 0.044), annual precipitation (p = 0.027), sunlight (p = 0.01) and CH. However, there was no significant relationship between the mean altitude above sea level (p = 0.6), land use (p = 0.4) and relative humidity (p = 0.24). Conclusions Based on the findings of this study, the incidence rate of CH in Isfahan province was higher than the average of the country. Moreover, among the geographical factors, climatic conditions, annual precipitation and sunlight were associated with CH.

Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions

Iodine intake must be boosted during pregnancy to meet the demands for increased production and placental transfer of thyroid hormone essential for optimal foetal development. Failure to meet this challenge results in irreversible brain damage, manifested in severity from neurological cretinism to minor or subtle deficits of intelligence and behavioural disorders. Attention is now being focused on explaining observational studies of an association between insufficient iodine intake during pregnancy and mild degrees of intellectual impairment in the offspring and confirming a cause and effect relationship with impaired maternal thyroid function. The current qualitative categorisation of iodine deficiency into mild, moderate and severe by the measurement of the median urinary iodine concentration (MUIC) in a population of school-age children, as a proxy measure of dietary iodine intake, is inappropriate for defining the degree or severity of gestational iodine deficiency and needs to be replaced. This review examines progress in analytical techniques for the measurement of urinary iodine concentration and the application of this technology to epidemiological studies of iodine deficiency with a focus on gestational iodine deficiency. We recommend that more precise definitions and measurements of gestational iodine deficiency, beyond a spot UIC, need to be developed. We review the evidence for hypothyroxinaemia as the cause of intrauterine foetal brain damage in gestational iodine deficiency and discuss the many unanswered questions, from which we propose that further clinical studies need to be designed to address the pathogenesis of neurodevelopmental impairments in the foetus and infant. Agreement on the testing instruments and standardization of processes and procedures for Intelligence Quotient (IQ) and psychomotor tests needs to be reached by investigators, so that valid comparisons can be made among studies of gestational iodine deficiency and neurocognitive outcomes. Finally, the timing, safety and the efficacy of prophylactic iodine supplementation for pregnant and lactating women needs to be established and confirmation that excess intake of iodine during pregnancy is to be avoided.

Agreement between markers of population iodine status in classifying iodine status of populations: a systematic review

BACKGROUND

Population iodine deficiency is indicated by >3% of the population with newborn thyroid-stimulating hormone (TSH) concentration >5 mIU/L, median urinary iodine concentration (MUIC) <100 µg/L, or >5% prevalence of goiter in school-age children. However, the agreement between these population markers has not been systematically investigated.

OBJECTIVE

To assess the agreement between TSH, MUIC, and goiter as markers of population iodine status.

METHODS

We performed a systematic search for studies published on PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, and PsycINFO up to 29 October, 2018. Studies assessing iodine status in the population using the TSH marker and either MUIC or goiter prevalence in school-age children were included. The agreement between markers in classifying iodine status of the population was assessed. The sensitivity and specificity of the TSH marker was determined against MUIC and goiter prevalence as the reference markers.

RESULTS

Of 17,435 records identified by the search strategy, 57 eligible studies were included in the review. The agreement between markers in classifying the iodine status of populations into the same category was 65% for TSH and MUIC, and 83% for TSH and goiter prevalence. The TSH marker had a sensitivity of 0.75 and specificity of 0.53 when compared with MUIC, and 0.86 and 0.50 when compared with goiter prevalence.

CONCLUSIONS

The TSH marker has a better agreement with goiter prevalence than MUIC when classifying the iodine status of populations. Re-evaluation of the current criteria for classifying the iodine status of populations using the TSH marker is warranted. This systematic review was registered at PROSPERO (http://www.crd.york.ac.uk/prospero/) as CRD42018091247.

Iodine consumption and cognitive performance: Confirmation of adequate consumption

Iodine, a dynamic nutrient present in thyroid hormones, is responsible for regulating thyroid function, supporting a healthy metabolism, and aiding growth and development. Iodine is also essential for brain development during specific time windows influencing neurogenesis, neuronal and glial cell differentiation, myelination, neuronal migration, and synaptogenesis. About 1.5 billion people in 130 countries live in areas at risk of iron deficiencies (IDs). Reduced mental ability due to IDs occurs in almost 300 million people. Ensuring the consumption of minimum recommended daily allowances of iodine remains challenging. The effects of ID disorders range from high mortality of fetuses and children to inhibited mental development (cretinism). Poor socioeconomic development and impaired school performance are also notable. Currently, ID disorders are the single greatest contributor to preventable brain damage in fetuses and infants and arrested psychomotor development in children. Iodized salt may help fulfill iodine requirements. Increases in food salt iodization programs can help overcome ID disorders. Dietary plans can be well adjusted to incorporate iodinated foods. Maternal iodine supplementation for offspring requires adequate attention. Fruits, vegetables, bread, eggs, legumes (beans and peas), nuts, seeds, seafood, lean meats and poultry, and soy products provide small quantities of iodine. Nutrient-dense foods containing essential vitamins and minerals such as iodine may confer positive effects. To some extent, fortified foods and daily dietary supplements can be provided for different nutrients including iodine; otherwise, iodine may be consumed in less than the recommended amounts. This review focuses on aspects of adequate iodine consumption to avoid cognitive impairments.