Effects of Thyroid Hormones on Brain Development: Cytoarchitecture and Neurodevelopmental Disorders

ABSTRACT Thyroid hormones (THs) are endocrine factors that play an important role in brain development by modulating several neurodevelopmental processes, including neuronal migration, synaptogenesis, and myelination. Therefore, adequate regulation of these hormones is important for the structure and function of the brain. Recently, a close association between THs deficiency or dysfunction has been found with several neurodevelopmental disorders, including autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). These results imply that thyroid hormones play an important role in the occurrence of neurodevelopmental disorders. In this review, we thoroughly investigate the biosynthetic pathways and regulatory mechanisms involved in thyroid hormones production. We also assess the importance of thyroid hormones during different periods of brain development, as well as the underlying molecular processes. Finally, we extend our discussion to explore the relationship between thyroid hormones and neurodevelopmental disorders. The objective is to provide mechanistic and clinical insights and to identify promising research avenues that could facilitate earlier diagnosis and intervention for these conditions.