Complex Interactions between Abnormal Thyroid Function and Neurodevelopmental Disorders: A Mendelian Randomization Study

Introduction: Neurodevelopmental disorders (NDDs), such as attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and tic disorders (TD), have been frequently investigated due to their profound impacts on social and emotional functions. In this regard, there is a new focus on the possible association between these disorders and thyroid dysfunction. The purpose of this study was to explore the relationship between NDDs and hyperthyroidism and hypothyroidism. Methods: In this study, we used MR analysis to explore the associations of ADHD, ASD, and TD with hyperthyroidism and hypothyroidism. MR analysis explores the associations between exposure and outcome using the Mendelian randomization framework and is based on extensive genomic datasets. Results: Our results suggested that hypothyroidism was associated with TD, while no individual genetic variant was associated with hypothyroidism, ADHD, or ASD. Additionally, we found no reliable evidence that ADHD, ASD, or TD were causally linked to hyperthyroidism. There was also no credible evidence that any individual genetic variant was associated with an increased risk of hyperthyroidism. Our findings remained robust in sensitivity analyses. Conclusion: Our study provides new insights into the relationship between NDDs and thyroid dysfunction. It suggests that there were potential risk factors and causal pathways and calls for early diagnosis, intervention, and integrated health care.