Disappearance of blocking type thyrotropin binding inhibitor immunoglobulin (TBII) during thyroid and steroid medication in a patient with autoimmune thyroiditis.

A 55 year-old female had suffered from 3 consecutive diseases for a year. The diseases were ulcerative colitis, primary hypothyroidism and idiopathic thrombocytopenic purpura, and had been treated with L-thyroxine (50 micrograms daily) and betamethasone (0.5 to 1.5 mg daily). On examination, the thyroid gland was not palpable at all, thyroid 99 mTc pertechnetate uptake was 0%, and an echogram revealed the existence of an atrophic gland. Thyrotropin binding inhibitor immunoglobulin (TBII) in the serum was elevated to 58.0% and her IgG almost completely inhibited the in vitro cAMP increase due to bTSH. After 5 months TBII turned out to be negative and the inhibitory IgG activity was reduced significantly. The thyroid gland also became visible scintigraphically. Thyroid medication was then stopped. Four months after the cessation of thyroxine, she felt quite well and her thyroid functions remained within the normal ranges. Antibody to Yersinia enterocolitica was positive at a low titer (X20) in the early stages, but elevated reciprocally with the fall in TBII and finally reached X320. In conclusion, evidence of the disappearance of blocking type TBII from the serum was demonstrated for the first time. Steroid might have caused some favorable effects, and this clinical report indicates the possibility that remission of hypothyroidism due to blocking type TBII can be expected.