Results: Antithyroid drugs are themain therapy formaternal hyperthyroidism. Bothmethimazole (MMI) and
propylthiouracil (PTU) may be used during pregnancy; however, PTU is preferred in the first trimester
and should be replaced byMMIafter this trimester.Choanal and esophageal atresia of fetus inMMI-treated and
maternal hepatotoxicity in PTU-treated pregnancies are of utmost concern. Maintaining free thyroxine
concentration in the upper one-third of each trimester-specific reference interval denotes success of therapy.
MMI is the mainstay of the treatment of post partum hyperthyroidism, in particular during lactation.