Painless Thyroiditis with Thyrotropin Receptor-blocking and Receptor-stimulating Autoantibodies

We herein report a rare case of a 41-year-old woman with painless thyroiditis who was positive for thyrotropin (TSH) receptor-blocking (TBAbs) and receptor-stimulating autoantibodies (TSAbs) in the thyrotoxic phase. Her serum thyroid hormone levels were high, and TSH was undetectable. The low uptake of (99m)Tc led to the diagnosis of painless thyroiditis. M22-TRAb, TBAb and TSAb were detectable in the thyrotoxic phase. Three months later, she became severely hypothyroid. M22-TRAb and TBAb were still strongly positive, although the TSAb levels had decreased to just above the reference range. In this case, TBAb led to hypothyroidism.