Assessment of intelligence quotient score in children at the age of six with suspected congenital hypothyroidism: A retrospective cohort study

Background: The clinical suspicion of Congenital Hypothyroidism (CH) is identified by abnormal results in the first test of Thyroid Stimulating Hormone (TSH) (5-9.9 mIU/L), and normal results in re-test (TSH<4 mIU/L). The CH has a contribution to physical and mental health. This study aimed to determine the Intelligence Quotient (IQ) score in children with suspected congenital hypothyroidism. Methods: This research is a retrospective cohort study conducted in Mashhad, Iran. The IQ scores of 1976 children at the age of 6 were considered as an outcome variable. The history of CH screening for each newborn was assessed, then all suspected CH newborns that diagnosed healthy in re-test were considered as an exposed group, the effects of this situation on IQ score was assessed using logistic regression. All analysis was performed in STATA. Results: The averages of IQ score (p<0.001), weight (p=0.024), and height (p<0.001) in the exposed group were lower than the unexposed group. The exposed group was related to those whose parental education was less or equal to 12 years (p<0.001). Similarly, the history of CH and maternal education for ≤12 years were detected as risk factors for having an IQ score of <90 in children. Conclusion: Aside from the link between parental education and clinical suspicion of CH in neonates, our findings underline the possible strong effect of CH status and maternal education for ≤12 years on reducing IQ scores in the next years of child life.