Thyroid hormone and disorders of the central nervous system

During the sensitive period of fetal and neonatal development, thyroid hormone deficiency leads to severe defects of the central nervous system (CNS), including mental retardation and movement defects. These clinical symptoms can be explained, based on animal studies, by a migration defect of cortical neurons as well as by reduced axonal connectivity. This review discusses the established knowledge in treating maternal and congenital hypothyroidism to avoid mental retardation. In addition, the findings on treating pregnant women and neonates with only borderline hypothyroidism are summarized. The differential diagnoses for more rare diseases of thyroid hormone resistance within the CNS (MCT8 defect), as well as defects of CNS development associated with thyroid diseases that have recently been described in children (Hashimoto's encephalopathy and NKX2.1 deficiency syndrome), are summarized as well.