Cause
The trigger for autoantibody production is unknown.
Since this autoimmune disease appears suddenly, often quite late in life, viral or bacterial infection may trigger antibodies that cross-react with the human TSH receptor (a phenomenon known as antigenic mimicry, also seen in some cases of type 1 diabetes). One possible agent is the bacterium Yersinia enterocolitica. However, evidence for the structural similarity between the bacterium and the human thyrotropin receptor, direct causative evidence is limited. Yersinia seems not to be a major cause of this disease, although it may contribute to the development of thyroid autoimmunity arising for other reasons in genetically susceptible individuals. It may only be an associated condition, with both having a shared inherited susceptibility. More recently the role for Y. enterocolitica has been disputed.
Some people may have a genetic predisposition to develop TSH receptor autoantibodies (HLADR, especially DR3, appears to play a significant role. Some of the eye symptoms of hyperthyroidism are believed to result from heightened sensitivity of receptors to sympathetic nervous system activity, possibly mediated by increased alpha-adrenergic receptors in some tissues.
Read more about this topic: Graves' Disease