Triiodothyronine (T3) concentration and therapy in autistic children.

The clinical and biochemical status of thyroid function of patients with an autistic syndrome was investigated. The study consisted of 13 patients between the ages of 7 and 21 years. There was no clinical evidence for hypothyroidism in any patient, and T3, T4, and TSH concentrations were within the normal range. Two patients who had retarded bone ages were treated with triiodothyronine for 6 months. Hyperthyroidism developed when T3 levels exceeded physiologic concentrations in these patients. The concept that the clinical response to triiodothyronine in autistic patients results from correction of thyroid dysfunction is not supported by these findings.