Antithyroid drugs during breastfeeding

Antithyroid drugs (ATDs) are widely used for the treatment of Graves' disease (GD) in the general population. Over the past decade, there has been an increasing awareness that several disturbances of thyroid function may occur in mothers after delivery which may be more prevalent than previously appreciated. Exacerbation of immune reactions occurs 3-12 month following delivery. Management of hyperthyroidism during lactation requires special considerations and should be implemented to prevent any adverse outcomes in mother and neonate. Continuation of breastfeeding is safe and should be encouraged in hyperthyroid mothers taking ATDs, whether these are ATDs being continued after gestation or indeed ATD treatment initiated in the postpartum period. Given PTU hepatotoxicity concerns, experts currently recommend using low-to-moderate MMI doses as a first-line therapy in lactating mothers. PTU should be reserved only as a second-line agent for cases of severe hyperthyroidism (thyroid storm) and allergic reactions to previous MMI treatment. ATD should be administered in divided doses immediately following each feeding. Evaluation of thyroid function tests is advisable at least 3-4 weeks after the initiation of breastfeeding.