The introduction of screening for congenital hypothyroidism has led to a marked improvement in neurodevelopmental outcome that has largely been attributed to the introduction of early treatment in the form of thyroxine. However, recent research has shown that the effect of hypothyroidism on the developing brain can result in specific developmental defects regardless of the early commencement of treatment. These defects consist predominantly of defective motor skills, clumsiness, learning difficulties, and behavior problems.