The authors investigated indices of hypothalamic-pituitary-thyroid (HPT) axis function in patients with social phobia. They found no differences between patients with social phobia and age- and sex-matched control subjects in plasma T3, T4, free T4, or TSH levels or in the proportion of subjects with positive antithyroid antibodies. Patients with social phobia and control subjects also did not differ in three of the four measures used to assess TSH response to TRH. These data suggest that abnormalities in thyroid function are not requisite neuroendocrine correlates of social phobia.