**3.2 Antithyroid drugs**

ATD represent the predominant therapy in Europe, Asia, and as a bridge therapy in the USA [17]. The thionamides, propylthiouracil (PTU), carbimazole (CBZ), and the active metabolite of the latter, methimazole (MMI) by inhibiting thyroid peroxidase enzymes they cause a decrease in thyroid hormone production. Moreover studies have shown that they have an immunosuppressive effect resulting in reduction of TSH-RAb levels, intercellular adhesion molecule-1 (ICAM-1) and soluble IL-2 receptor (sIL-2R) [18]. ATD are indicated especially in younger patients and in cases when a short term treatment is needed prior to RAI or surgery. Moreover, patients with mild disease (small size of goiter, negative or low TRAb values), of old age with comorbidities who are at high risk of postoperative complications or patients with a history of head and neck irradiation or surgery, are candidates for ATD therapy. In pregnancy ATD are the first line therapy for GD. Also ATD are indicated, in cases of people receiving care in nursing facilities and therefore radiation safety precautions cannot be preserved, in patients with moderate to severe active Graves' orbitopathy (GO) and in those who need more rapid biochemical disease control. Finally, ATD should be considered when there is lack of access to an experienced thyroid surgeon [12]. Adverse events of antithyroid medication range from milder adverse events such ascutaneous eruptions, gastrointestinal disorders and arthralgias to more serious complications as agranulocytosis, frank polyarthritis and hepatotoxicity. Adverse events of methimazole seem to be dose related (40 mg/day or more) while such thing has not been associated pylthiouracil doses [19].
