BEHAVIORAL-EFFECTS OF LIOTHYRONINE (L-T-3) IN CHILDREN WITH ATTENTION-DEFICIT HYPERACTIVITY DISORDER IN THE PRESENCE AND ABSENCE OF RESISTANCE TO THYROID-HORMONE

Evidence that the thyroid may play a role in the pathogenesis of atten tion deficit hyperactivity disorder (ADHD) comes from observations tha t 48% to 73% of children with the syndrome of resistance to thyroid ho rmone (RTH) have ADHD. Casual observations in subjects with RTH have s uggested that treatment with thyroid hormone may improve the symptoms of ADHD. The aim of this study was to determine whether thyroid hormon e has a beneficial effect on the behavior of children with RTH. A pros pective, randomized, double-blinded, placebo-controlled, cross-over st udy was conducted to evaluate the effect of the rapid acting thyroid h ormone, liothyronine (L-T-3), on the behavior of 8 children with ADHD + RTH, and 9 children with ADHD and normal thyroid function (ADHD Only ). Parent and teacher ratings of hyperactivity (Conners scale) and a c omputerized continuous performance test (CPT) were used as objective m easures of hyperactivity, attention and impulsivity. L-T-3 had no effe ct on Conners Hyperactivity Index in 7 of 9 children with ADHD Only; i t caused improvement and deterioration in 1 subject each. In contrast, the rating in 5 of 8 subjects with ADHD + RTH showed improvement, whe reas 3 of 8 subjects remained unchanged. L-T-3 was associated with inc reased commission errors in 5 of 8 children with ADHD Only and decreas ed commission errors in 4 of 7 with ADHD + RTH. In children with RTH a nd ADHD, particularly those that exhibit hyperactivity, L-T-3 in supra physiological doses may be beneficial in reducing hyperactivity and im pulsivity. In the majority of children with ADHD who do not have RTH, L-T-3 treatment has no effect or may be detrimental.