Hashimoto’s hyperthyroidism may present with a high TRAb, but it is relatively rare. TRAb, or TSH (thyroid-stimulating hormone) receptor antibodies, consist of stimulatory (TSAb) and inhibitory (TSBAb) antibodies, with TSAb activating TSH and increasing thyroid hormone secretion, as opposed to TSBAb inhibiting TSH and suppressing thyroid hormone secretion. Elevated TRAb is an important indicator for the diagnosis of Graves’ disease (diffuse toxic goiter). It may also be elevated in patients with Hashimoto’s thyroiditis, but is generally lower than in patients with Graves’ disease and is less common. Hashimoto’s thyroiditis is an autoimmune thyroiditis, and abnormal thyroid autoantibodies, TPOAb (thyroid peroxidase antibody) and TgAb (thyroglobulin antibody), are the main causative factors in Hashimoto’s thyroiditis. TPOAb and TgAb cause damage to thyroid cells and the release of stored thyroxine into the bloodstream.TRAb may also be involved in the development of Hashimoto’s hyperthyroidism, the mechanism of which is unclear. Hyperthyroid Hashimoto’s thyroiditis often requires a differential diagnosis with Graves’ disease, and antibodies such as TRAb, TPOAb, and TgAb may be used to differentiate between the two. It is recommended that patients with elevated TRAb be further investigated for other thyroid autoantibodies and thyroid function to identify the cause of the disease.