Investigation of risk factors for congenital hypothyroidism (CH) using a population-based case-control study as part of the 2015-2018 screening program in Kohgiluyeh and Boyer Ahmad province in southwestern Iran

Abstract

Introduction and objectives: Congenital hypothyroidism (CH) is a lack of thyroid hormone at birth, crucial for brain development. A nationwide screening program has been implemented in Iran since 2005, resulting in over 12 million infants being screened and more than 30,000 patients diagnosed and treated. The incidence of CH in Iran is 2.7 per thousand live births, which is higher compared to the global incidence of 1 in 3,000 to 4,000. The incidence of CH in Kohgiluyeh and Boyer Ahmad province is significantly higher than the national and global incidence. Prognostic factors including twins, the season of birth, puberty, jaundice at birth, birth weight, gestational age, anemia and goiter of the mother, type of delivery, father's education, and smoking status are significantly associated with CH. Genetic, climatic, and environmental factors also play a role in the development of CH. Congenital hypothyroidism (CH) is one of the most common causes of intellectual disability, which can be prevented if diagnosed and treated on time. We aimed to investigate some related risk factors for CH in infants born in Kohgiluyeh and Boyer Ahmad province. Results: This was a population-based case-control study conducted on 270 infants. The study population included infants who were born between 2015 and 2018 and were subjected to a screening program for CH. In general, 135 infants diagnosed with CH who were confirmed by a specialist and had a medical record were considered as the case group and the rest (135 infants) who were healthy were considered as controls. Patients and control infants were matched in a one-to-one ratio. Information was extracted from the Sib Health Integrated System (http://sib.yums.ac.ir). Regression analysis using the logistic regression method was performed on data collected from a sample of 270 infants and SPSS software version 24 was used to analyze the data with P<0.05 considered significant. Ethical considerations were addressed by obtaining approval from the ethics committee of Yasuj University of Medical Sciences under ethical number IR.YUMS.REC.1397.136 and holding preliminary meetings with authorities, health, and medical personnel to discuss different tasks, collaboration, and completion of checklists. Conclusion: The results of the study show that among the cases studied, 3 factors, weight and height of the infant at birth and a family history of the disease in the infant could be the main risk factors for hypothyroidism (CH) in this province. Other factors such as birth order (rank), maternal age, maternal weight and height, age and mode of delivery, history of medication and iodized salt intake in the mother, diseases of the mother and father, and familial relationship of the parents were not observed to have a statistically significant association with CH. further studies are needed to analyze the results of the present study to establish the causality of these associations with greater certainty. Keywords: Neonatal hypothyroidism, risk factors, case-control study, screening, Kohgiloyeh, and Boyer Ahmad, Iran