Thyroid storm is associated with high mortality (8%-25%), although there has been a paucity of large epidemiologic studies due to rarity of the diagnosis.1 Treatment for thyroid storm includes thionamides (propylthiouracil, methimazole, or carbimazole, which is metabolized to methimazole) to inhibit the enzyme thyroid peroxidase in the thyroid, thus reducing the synthesis of triiodothyronine (T3) and thyroxine (T4). This evidence concerns the gene TPO and thyroid crisis.