A high rate of attention deficit/hyperactivity disorder (ADHD), of which the major symptoms are hyperactivity, inattention, and impulsiveness, is observed in children with iodine deficiency, which causes TH insufficiency [24,39] and in children with resistance to TH [15] that is caused by mutation of a TH receptor beta isoform (TRβ) [32]. The gene discussed is THRB; the disease is attention deficit-hyperactivity disorder.