The behavioral characteristics of 63 children with early-treated congenital hypothyroidism (CH) were evaluated by parent and teacher ratings and compared to 34 healthy controls (ages 7.5-9.5 yrs) at the University of Jyvaskyla, Finland. Children with CH, especially those with thyroid agenesis, were more introverted, insecure, and isolated, and showed more motor clumsiness, rather than social negativity and inattention. Children with thyroid agenesis were clumsier than those with thyroid dysgenesis. It is suggested that the motor problems contribute to the introverted behavior. The more severe the thyroid deficiency, the greater probability for behavior problems. The lack of effect on attention challenges claims of an association between ADHD and thyroid dysfunction. 
COMMENT. Early-treated congenital hypothyroidism is associated with introverted behavior and motor clumsiness, and not inattention, impulsivity, and hyperactivity, the core symptoms of ADHD.