Spatial analysis of Neonatal Congenital Hypothyroidism and Nitrate as an environmental pollutant in Isfahan Province during 2010-2013

Abstract

Background:Thyroid absorption of iodine could be encumbered by nitrate drinking water when it is transported to the fetal thyroid gland. Therefore, nitrate potentially causes congenital hypothyroidism (CH) due to thyroid dysfunction. In this study, we have not only aimed at spatial determination of CH distribution and nitrate concentration (NC) existing in drinking water, but also we intended to evaluate the probable impact of nitrate on CH incidence.Methods:Annual average of nitrate in drinking-water as well as number of CH infants diagnosed through the screening program were applied to determine the incidence ratio of the disease for each town (from 2010 to 2013). Afterward, Arc GIS 9.3 was used to draw choropleth maps with quantile classification. Data were entered into SPSS 16.0 and Excel 2010 software. Finally, linear regression was applied for data analysis.Results:The incidence rate of CH (considering transient and permanent cases) was about one in every 413 births. Khansar, Golpaygan, Naein, and Ardestan had the highest incidence rate of CH respectively. On the other hand, Tiran, Dehaghan, Khansar, and Fereydan had the highest level of nitrate drinking water. There was a strong relationship between the NC and incidence of CH in Khansar; however, this relationship was not significant (P = 0.392) in Isfahan province.Conclusions:Since there was not a significant relationship between NC in drinking-water and incidence of CH through linear regression analysis, more studies should be implemented to confirm or refute our observations.

A Systematic Review on the Risk Factors of Congenital Hypothyroidism

“…They concluded that ClO 2 was a risk factor for CH in preterm and low-birth-weight neonates (26). In another study in Iran, Mehrnejat et al found no significant relationship between nitrate concentration in drinking water and the incidence of CH through linear regression analysis (58).…”

“…Some of the reported risk factors, including environmental pollutants (25,58), dietary component of mothers during prenatal period (41,64), neonatal jaundice (47), maternal anemia (48), intrauterine growth retardation (6), lower weight gain during pregnancy (60), urbanization (62), parental occupation and education (35,47), gestational diabetes (6,46,59), and smoking (14,47,60) have limited evidence. It seems that more studies for investigating the association of the mentioned risk factors with CH are necessary.…”

Mapping the relative risk of congenital hypothyroidism incidence via spatial zero-inflated poisson model in Guilan Province, Iran

“…According to the results, there was no significant relationship between nitrate concentration in water and CH incidence. [ 25 ]…”

Effects of Geophagy on Hemoglobin Level and Iodine Absorption /Assimilation in Albino Rats

“…Furthermore, persistence or residual goiters have also been observed in post-salt iodization phase in a community with a goitrogen [43], indicating the effect of goitrogens in adequate iodine prophylaxis. In addition, authors reveal that moderate intake of iodine, adequate to meet iodine requirement, may not ensure normal functioning of thyroid in the presence of goitrogens [44], a situation that is obvious during the consumption of contaminated kaolin.…”