Attention Deficit and Hyperactivity Disorders due to Iodine Deficiency: A Novel Iodine Deficiency Disorder Affecting the Offspring of Hypothyroxinemic Mothers

Attention deficit and hyperactivity disorder (ADHD) is a developmental syndrome characterized by difficulties in sustaining attention and hyperactivity. This neurobehavioral disorder has been reported in children with generalized resistance to thyroid hormone (GRTH) and is attributed to brain deprivation of the hormone. Analogously, we hypothesize a similar mechanism to be responsible for the high (70%) prevalence of ADHD affecting children living in mild-tomoderate iodine deficiency (ID) areas. ID-related ADHD could be due to an inadequate supply of maternal thyroxine to the fetal brain, development of which would therefore suffer from varying degrees of maternal thyroid failure during the first phases of neurogenesis. Indeed, ADHD prevalence was even higher (almost 90%) in children born to mothers who experienced hypothyroxinemia (low FT4 with normal TSH) at early gestation. Therefore, ADHD should be considered as a novel ID disorder affecting intellectual ability. This evidence further emphasizes the need for intensive programs of iodine prophylaxis to prevent/correct ID-related early gestational hypothyroxinemia promptly.