A patient with Graves' disease who developed hypothyroidism associated with thyroid stimulation blocking...

A girl, 12 years of age, developed Graves' disease compounded with rheumatic fever and idiopathic thrombocytopenic purpura. Thrombocytopenia improved under short-term treatment with steroids and her mitral valvular insufficiency, due to the rheumatic fever, disappeared 4 years later. Initially, she had been treated with propylthiouracil (PTU) for 28 months. She suffered a relapse 9 months after stopping PTU and so she was given further PTU therapy. However, hypothyroidism developed 11 months after the initiation of therapy and continued, though further PTU treatment was discontinued. She now receives 1-thyroxine and maintains a euthyroid state. At the onset of the patient's hyperthyroidism, the TSH-binding inhibitor immunoglobulin (TBII) and the thyroid stimulating antibodies (TSAb) were found to be positive. During the remission period, only the thyroid stimulation blocking immunoglobulin (TSBI) was weakly positive. At relapse, only TBII was mildly positive. When hypothyroidism developed, both TBII and TSBI were positive, and TSAb was negative in all testings of her diluted IgGs. The patient's TBII and thyroid dysfunction were unaffected by high-dose intravenous gammaglobulin therapy or by treatment with prednisolone 0.5 mg/kg/day for 2 weeks. In conclusion, the emergence of TSBI during or after anti-thyroid drug therapy might possibly lead to hypothyroidism in patients with Graves' disease.