Clinical thyrotoxicosis in Graves' disease patients is caused by thyrotropin receptor (TSHR)-stimulating autoantibodies. The molecular mechanisms of TSHR post-translational modification, TSHR signaling and TSHR-autoantibody interaction are still debatable, and the precise interaction of stimulating and blocking autoantibodies with TSHR is unclear. Recent TSHR epitope studies indicate that binding sites for stimulating and blocking autoantibodies are close together, not on distinct or distant parts of the molecule. Furthermore, new methods to detect TSHR autoantibodies and their clinical use are addressed. Highly sensitive TSHR autoantibody assays are widely available and cost efficient, and their routine clinical use might help in the differential diagnosis of hyperthyroidism and disease outcome prediction in patients with high levels of TSHR autoantibodies.