Which condition is associated with hyperthyroidism and characterized by exophthalmos?

Graves' disease is the primary condition associated with hyperthyroidism and is specifically characterized by the presence of exophthalmos, which is the protrusion of the eyes. This autoimmune disorder leads to the overproduction of thyroid hormones, resulting in symptoms such as weight loss, rapid heartbeat, and anxiety, in addition to the distinctive eye changes. The exophthalmos occurs due to swelling and inflammation of the eye muscles and surrounding tissues, a response to the autoimmune activity directed against the thyroid gland.

In contrast, Hashimoto's disease is primarily characterized by hypothyroidism due to the destruction of thyroid tissue, while Cushing's syndrome and Addison's disease are disorders related to adrenal hormone imbalances and do not typically exhibit the features of hyperthyroidism or exophthalmos. Therefore, the link between Graves' disease and the specific symptom of exophthalmos confirms it as the correct choice.