Introduction: The thyroid hormones have an important effect on the development and maturation of the mammalian central nervous system before and after birth. Thyroid hormones, triiodothyronine and thyroxine, adjust the processes of brain differentiation, such as synaptogenesis, dendritic and axonal growth, migration of neuronal cells and myelination. Any impairment in thyroid function and changes in the supply of thyroid hormones during development of nervous system leads to severe and irreversible alterations in the structure and function of the brain. Timing and duration of thyroid hormone deficiency affect development of different parts of the central nervous system. However, Neurological symptoms are commonly observed in adulthood with both hyperthyroidism and hypothyroidism. Conclusion: Understanding the mechanisms of the effect of thyroid hormones on embryo and adult neurogenesis is essential for improving the treatment of neurological disorders.