Study of Thyroid Function in Children with Attention Deficit Hyperactivity Disorder and Aggressive Behavior
Background: Attention deficit hyperactivity disorder (ADHD) is a well recognized psychiatric disorder of childhood. Its cause is unknown, but there is evidence of familial predisposition. Symptoms suggestive of the disorder have been reported in patients with generalized resistance to thyroid hormones (GRTH), a disease caused by a mutation in the thyroid receptor beta gene and characterized by reduced responsiveness of peripheral and pituitary tissues to thyroid hormone actions. Aim of the Work: This study was conducted to assess the frequency of thyroid hormone abnormalities in children with ADHD and/or aggressive behavior and to relate these abnormalities to the type of behavioral disorder. Patient and Methods: Thirty cases with behavioral disorders (ADHD and/or aggression) diagnosed by DSM-IV classification were studied in comparison to 10 age-and sex-matched healthy controls. Clinical examination and psychiatric evaluation including IQ and psychosocial assessment were done to all patients. Measurement of serum free triiodothyronine (fT3), free tetraiodothyronine (fT4) and thyrotropin (TSH) was done to cases and controls. Results: There was a significantly lower IQ (p<0.05) among patients (84.2±16.4%) when compared to controls (100.9±5.4%). Significantly higher mean fT3 and TSH levels (p<0.05) were detected among cases (5.96±2.9 pg/ ml and 6.53±3.2 uIU/ml respectively) when compared to controls (2.96±0.82 pg/ml and 2.28±1.28 uIU/ml respectively) while a non significant difference (p>0.05) in the fT4 level was detected. Twelve out of our 30 studied cases (40%) had thyroid hormone resistance among whom 7 (23.3%) had high fT3 and high TSH levels while 5 (16.7%) had high fT3 and normal TSH. Among the ADHD group, 3/16 (18.8%) had high fT3 and high TSH levels and 1/16 (6.3%) had high fT3 and normal TSH levels. Among those with aggression, 2/8 (25%) had high fT3 and high TSH and a similar percentage had high fT3 and normal TSH. Among those with both ADHD and aggression, 2/6 (33.3%) had high fT3 and high TSH and a similar percentage had high fT3 and normal TSH. In the 3 groups of behavioral disorders, none of the cases had high fT4 levels above the age-matched controls. Conclusion: A significant number of patients meeting the diagnostic criteria for ADHD have associated RTH. Therefore, measurement of TSH and fT3 should be incorporated in the work up of children in families having ADHD and/or aggression. In children with ADHD and concomitant RTH, particularly those who exhibit hyperactivity, liothyronine (L-T3) in supraphysiological doses could be beneficial in reducing hyperactivity and impulsivity and thus decreasing the need for psychostimulants. Further studies are warranted regarding the role of RTH in the pathophysiology of ADHD.
Keywords: ADHD, aggression, thyroid, resistance.
Egypt. J. Hum. Genet Vol. 9 (1) 2008: pp. 93-104