Exophthalmos is defined as a protruding eyeball anteriorly out of the orbit. This disorder is often associated with which of the following?

In Graves' disease, there is a hyperthyroidism due to stimulating autoantibodies to the TSH receptor which continuously mimic the effect of TSH but which are not subject to the feedback mechanisms which lower the level of TSH once sufficient thyroid hormone has been produced. Graves' disease is often associated with exophthalmos, which involves marked hypertrophy of the extra-occular muscles. This association may be caused by autoantibodies against an antigen present on both eye muscle and thyroid.