THYROID-HORMONES CORRELATE WITH SYMPTOMS OF HYPERACTIVITY BUT NOT INATTENTION IN ATTENTION-DEFICIT HYPERACTIVITY DISORDER

The diagnostic validity of dividing attention deficit hyperactivity di sorder (ADHD) into two distinct subgroups, one with and one without hy peractivity, is controversial since there have been no physiological d ifferences demonstrated between these two subgroups. In this study, th e relationship between thyroid hormones and symptoms of hyperactivity was examined in subjects with resistance to thyroid hormone (RTH) and their unaffected family members. Clinical data were collected on 152 s ubjects; 75 subjects with RTH and 77 family members without RTH. Each subject was assessed using DSM-III-R criterion based, structured psych iatric interviews, and Total T3 (TT3), Total T4 (TT4) and TSH concentr ations were measured. The total number of ADHD symptoms were assigned to either inattention or hyperactivity subgroups using DSM-III-R crite ria. The total number of ADHD symptoms were then reassigned to inatten tion or hyperactivity/impulsivity subgroups using DSM-IV criteria. Pea rson R correlation coefficients were calculated separately for the RTH and unaffected family members groups in order to determine the relati onships between TSH, TIT and TT4 concentrations, and the DSM-III-R and DSM-IV symptom categories of ADHD in both groups. TSH concentrations were not significantly correlated with any of the symptom categories i n either group. However, in the RTH group, both TT3 and TT4 concentrat ions were significantly and positively correlated with total symptoms of ADHD (DSM-III-R) as well as symptoms of inattention (DSM-III-R) and symptoms of hyperactivity (DSM-III-R). When DSM-IV criteria were used , which reassigns symptoms of impulsivity from the inattention to the hyperactivity category, only the positive correlation between TT3 and TT4 concentrations and symptoms of hyperactivity/impulsivity (DSM-IV) remained significant. In the group of unaffected family members, the r elationship between TT3 concentrations and symptoms of hyperactivity/i mpulsivity (DSM-IV) was the only significant correlation. The data sup port the hypothesis that thyroid hormones may provide a physiological basis for the dichotomy between symptoms of inattention and symptoms o f hyperactivity, particularly when DSM-IV criteria are applied.