Investigation of the incidence rate and geographical distribution of congenital hypothyroidism in the newborns in Ilam Province by using geographic information system (GIS) between 2006 and 2016

Background and Aim: Congenital hypothyroidism is an endocrine disorder and is one of the main causes of mental retardation in the newborns. Genetic, environmental and geographical factors are associated with the disease. This study aimed to evaluate the incidence rate and correlation of geographical factors with congenital hypothyroidism in Ilam Province. Materials and Methods: This study was a descriptive analytical study and evaluated the incidence rate and geographical distribution of congenital hypothyroidism in the newborns in Ilam Province from the beginning of 2006 to the end of 2016. We studied the results of heel samples of the newborns between 3 to 5 days of age who had been screened for congenital hypothyroidism in the referral laboratories of the health centers of the health department of the Ilam University of Medical Sciences in all cities of Ilam Province. We used ArcGIS (ver 10.3) software for evaluation of geographical distribution. Statistical tests of Poisson regression and scatter plot were used to investigate the relationship between geographical factors and the incidence rate of congenital hypothyroidism. Data analysis was performed by use of SPSS 16 software. Results: Based on the findings of the screening of 106900 newborns born in Ilam Province, the incidence of congenital hypothyroidism in this study was 2.61 in 1000 live births (2.7 male newborns / 1000 live births, and 2.48 female newborns / 1000 live births). Among all the patients 55.4% were male and 44.6% were female. There was a significant correlation between the mean annual rainfall and herbal coverage with congenital hypothyroidism (p<0.05). Mean annual temperature, sunlight and relative humidity had no significant relationship with the disease (p>0.05). Conclusion: Based on the findings of this study, incidence of congenital hypothyroidism is high in Ilam Province. Abdanan and Ilam cities had the highest incidence rates of hypothyroidism and are among the high risk hotspots of the disease. As a result, authorities should take appropriate measures in order to control and reduce the incidence of this disease in the province. Also, among the geographical factors, the mean annual rainfall, herbal coverage and sunlight were associated with congenital hypothyroidism.