[Transitory efficacy of potassium perchlorate in hypothyroidism caused by amiodarone]

We report a case of a patient with hypothyroidism due to amiodarone. The short-term administration (1 g/die for 10 days) of potassium perchlorate (KClO4) led to normalization of serum thyroid hormone concentrations and marked reduction of thyrotropic hormone. The reduction of KClO4 (400 mg/die) and its following withdrawal led to reappearance of hypothyroidism signs. No side-effects or toxic reactions occurred during KClO4 therapy. This anion competitively inhibits thyroid iodide transport, reducing intrathyroidal iodide content and removing thyroid hormone synthesis inhibition. We suggest KClO4 therapy when amiodarone-associated hypothyroidism impairs a pre-existent cardiac disease and when a quick restoration of euthyroidism is necessary. Nevertheless, we emphasize that its effect can be transitory in cases of short-term treatment or low doses.