Evaluation of developmental toxicity of propylthiouracil and methimazole.

Background: Propylthiouracil (PTU) and methimazole (MMI) are antithyroid drugs used to treat hyperthyroidism. Despite the widespread use of PTU and MMI during pregnancy, modest clinical data and less animal data are available on the teratogenic potential of these drugs.

Methods: We evaluated the teratogenicity of in utero exposure to PTU or MMI in mice and rats.