Thyroid autoimmunity in chronic idiopathic urticaria: implications for therapy.

The association between thyroid autoimmunity and chronic idiopathic urticaria has long been recognized, although prevalence rates differ in the studies reported to date (from 12 to 29%). There is, therefore, a strong indication to screen patients affected by chronic urticaria of unknown origin for thyroid antibodies (antithyroperoxidase and antithyroglobulin) and, when positive, for serum thyrotropin to assess thyroid functional status. Less clear is the implication of thyroid autoimmunity for therapy, as most patients with urticaria who have associated thyroid autoimmunity are euthyroid. There is no doubt that cases with clinical or subclinical thyroid dysfunction should undergo treatment with either levothyroxine or antithyroid drugs for hypo- or hyper-function, respectively. Although the best remission rates for symptoms of urticaria have so far been obtained with levothyroxine in patients who are euthyroid, monitoring of thyroid function through serum thyrotropin determination is highly recommended because of the risk of hyperthyroidism, especially in the elderly.