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

Abstract

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.

Shift in Dominance from Blocking to Stimulating Type of Thyrotropin Receptor Antibodies, Resulting in Conversion from Hypothyroidism to Hyperthyroidism during Late Pregnancy

“…Using a porcine thyroid cell cAMP system, TSAb enzyme immunoassay (EIA) was measured with a TSAb kit for EIA bioassay (Yamasa Corporation, Chiba, Japan), according to the manufacture's instruction until July 2022 ( 5 , 8 ). This bioassay specifically stimulated TSAb activation via wild-type receptor expression on cultured porcine thyroid cells.…”

“…Using the same porcine thyroid cell AMP system, TBAb activity was assayed by measuring the ability of patient sera to prevent bovine TSH from stimulating cAMP production in comparison to the control serum response ( 5 , 9 ). The estimated cut-off value of TBAbs is 34%, and the intra- and interassay CVs ranged between 1.2-7.4% and 1.3-5.3%, respectively.…”

“…FT4, FT3, and TSH values were measured by an electrochemiluminescence immunoassay (cobas e 411 plus; Roche Diagnostics, Manheim, Germany) (5). TBII levels were measured by a second-generation TRAb assay until September 2017 (6) and subsequently, by an M22-TRAb thirdgeneration assay (7).…”