Recent evidence confirms that antibodies to the TSH receptor (TRAb) are central to the pathogenesis of both Graves’ disease itself and TED. Major advances have been made in recent years in the laboratory tests used to measure TRAb levels. However, reliable automated measurement of TRAb in a form relevant to clinical management is challenging because TRAb that activate the receptor need to be distinguished from TRAb that block the receptor or simply bind but do not block the receptor. Furthermore, TRAb that activate the TSH receptor on thyroid cells may be different from the antibodies that activate the receptor in the retro-orbital tissue in TED. Modern TRAb assays are now very reliable at confirming the diagnosis of Graves’ disease in hyperthyroid patients. However, they are less sensitive or specific when applied to diagnosis of TED and are not yet sufficiently reliable to replace clinical evaluation in the diagnosis and management of TED.