ATTENTION-DEFICIT HYPERACTIVITY DISORDER AND THYROID-FUNCTION

Attention-deficit hyperactivity disorder (ADHD) is thought to have a b iologic basis, but the precise cause is unknown. It is one of the neur odevelopmental abnormalities frequently observed in children with gene ralized resistance to thyroid hormone (GRTH), suggesting that thyroid abnormalities may be related to ADHD. We report a prospective screenin g study for thyroid abnormalities in 277 children with ADHD by measure ment of serum levels of total thyroxine, free thyroxine index, and thy rotropin. Fourteen children with ADHD had thyroid function test abnorm alities: six had o normal free thyroxine index and elevated thyroxine level (group 1); three had a high free thyroxine index and a normal th yrotropin level (group 2); and five hod a low free thyroxine index wit h a normal thyrotropin level (group 3). GRTH could not be demonstrated in a detailed study of four of the subjects in whom it was suspected (groups 1 and 2). Although the prevalence of ADHD in subjects with GRT H has been reported to be 46%, the overall prevalence of GRTH must be less than i:2500 because we failed to detect GRTH in the 277 children with ADHD studied. We conclude that the prevalence of thyroid abnormal ities is higher (5.4%) in children with ADHD than in the normal popula tion (<1%).