Chronic idiopathic urticaria (CIU) is well known to be associated with antithyroid peroxidase antibodies and autoimmune thyroiditis.
Coexisting Graves disease has only rarely been observed. We describe 2 patients with CIU who developed autoimmune hyperthyroidism with antithyrotropin receptor antibodies. Antithyroid peroxidase antibodies were also present in 1 of the patients, but both responded poorly to high-dose antihistamine therapy. Both patients improved signifi cantly, and their thyroid function recovered with carbimazole.
We advise clinicians to be alert to the symptoms of hyperthyroidism when patients with CIU respond poorly to antihistamine therapy, as prompt treatment of hyperthyroidism significantly improves urticaria.

Key words: Chronic urticaria. Graves disease.