Antithyroid drugs used in the treatment of hyperthyroidism during breast feeding. An update and new perspectives.

Antithyroid drugs (ATD) are widely used by endocrinologists all over the world for the treatment of Graves’ disease (GD) in the general population and in lactating thyrotoxic mothers. Traditionally, these agents produce minor side effects (rash, fever, urticaria) in 5-10% of the treated patients and major side effects (agranulocytosis, vasculitis, hepatic toxicity) much less frequently. These side effects appear more likely to be dose-related for methimazole (MMI) rather than propylthiouracil (PTU). To our knowledge, there are no specific data regarding the occurrence of minor side effects that might occur in lactating thyrotoxic mothers under ATD. Nevertheless, daily clinical practice has usually shown these side effects to be reversible after dose adjustment.