Bioassays for TSH-receptor autoantibodies: an update

Immunoglobulins in patients with Graves' disease (GD) that modulate the thyroid stimulating hormone receptor (TSH-R) do so via stimulating cAMP dependent signals (TSI), blocking TSH or inhibition of TSH-receptor activation (TBI) or inducing apoptotic signals. These functional immunoglobulins represent powerful biomarkers of anti-self reactivity in the thyroid and systemic tissues that harbor TSH-R expressing target cells. TSI on thyrocytes induce hyperthyroidism, and TSI on TSH-R fibroblasts of orbital muscles, skin and heart provoke the release of cytokines and antigen-specific T-cell responses leading to systemic inflammation. Bioassays of anti-TSH-R autoantibodies provide decisive information on GD activity. This review examines the past and present bioassays in GD. The critical goal of cell-based anti-TSH-R autoantibody bioassays, to identify the pathogenic immunoglobulins in GD under robust and standardized conditions suitable for routine clinical laboratory practice, is discussed.