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.

Background: This study was designed and conducted to investigate the spatial distribution of permanent and temporary congenital hyperthyroidism (PCH and TCH) in Isfahan. Methods: This study was conducted on neonates who were born from March 21, 2006 to March 20, 2011 and had undergone the congenital hypothyroidism (CH) screening program in counties affiliated to the Isfahan University of Medical Sciences. CH was diagnosed in 958 patients who treated with levothyroxine. The incidence rates of permanent and temporary congenital hypothyroidism in Isfahan province were calculated and their distribution was shown on the map. The space maps were drawn using the ArcGIS software version 9.3. Results: Based on the data obtained from the screening program, the average incidence of congenital hypothyroidism in the province during the period of 2006–2011 was 2.40 infants per 1000 live births (including both PCH and TCH). The most common occurrence was in Ardestan County (10:1000) and the lowest overall incidence was observed in the Fereydounshahr county (1.39:1000). The incidence of PCH in the counties of Ardestan and Golpayegan had the highest rate in all years of study; and the greatest number of TCH cases in the five years were observed in Nain, Natanz, Khansar and Chadegan counties. Conclusion: Adding the time dimension and performing spatial-temporal analysis is suggested because of the following items: high prevalence of CH in Isfahan province, the important role of this disease in mental retardation and neuropsychiatric disorder, the necessity of conducting future medical researches to find possible factors of CH etiology in Isfahan province, as well as necessity of performing spatial analysis with advanced statistical methods.

The aim of this current study is to investigate the association between familial and environmental factors and prevalence of congenital hypothyroidism (CH) in Isfahan province. In this retrospective cohort study, data of the neonates referred for CH screening in different cities of Isfahan province were evaluated. Data regarding air and soil (lead, cadmium) pollutants were collected. The spatial association between mentioned environmental pollutants and prevalence of CH in different cities of Isfahan province was evaluated by using GIS software, and multilevel linear regression was used for evaluating the levels of environmental pollutants and neonates' serum TSH. During the study period, 389,945 neonates were screened, from which 934 diagnosed with CH (1 in 417 neonates).The prevalence rate of CH was ranged from < 20 in 10,000 live births to > 45 in 10,000 live births in different cities of Isfahan province. There was no any significant association between level of soil lead and cadmium and air pollutants with prevalence of CH in different cities of Isfahan province (P > 0.05).There was a significant positive association between soil cadmium and air pollution evaluated by air quality index (AQI) and level of screening serum TSH in CH patients. Considering the significant association between cadmium and AQI with first serum TSH, it is inferred that the interaction of genetic, autoimmune, familial, and environmental factors with each other could influence on neonatal thyroid function. It seems that the role of some mentioned component is more prominent which should be investigated in future researches.

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