There is a high prevalence of thyroid autoimmunity in patients with chronic urticaria. The patient with urticaria and anti-thyroid antibodies may be euthyroid, hyperthyroid or hypothyroid. The mechanism of the association is poorly understood. The Thyroid and Urticaria is a review of the topic in the October issue of Current Opinion in Allergy and Clinical Immunology.
Some patients may achieve remission with L-thyroxine, which of course is indicated for those who are hypothyroid. Such treatment of euthyroid patients is not supported by high level evidence and is controversial.
Thyroid testing should be considered in patients with chronic urticaria. Knowledge of this association could help a patient and might come in handy some day on internal medicine boards.