Circulating TSH-binding inhibiting immunoglobulins in myasthenia gravis

Using a radioligand receptor assay the sera of 46 patients with myasthenia gravis (MG) were tested for the presence of circulating TSH-binding inhibiting immunoglobulins (TBII). In addition thyroid function was evaluated on the basis of T3, T4, TBG and TSH radioimmunoassays including the TRH stimulation test. Circulating antimicrosomal and antithyroglobulin thyroid antibodies were measured by haemagglutination techniques. Two patients had concomitant Graves' disease (GD), 5 were euthyroid with autonomously functioning thyroid tissue due to non-immunogenic multinodular goitre and 39 myasthenic patients were euthyroid with normal pituitary thyroid axis. Only 1 patient with GD had strongly positive TBII-activity and 3 euthyroid MG patients were TBII borderline-positive.