A case is described here of a young euthyroid woman with a goitre and hearing impairment. Perchlorate discharge test showed increased washout of iodine. Genetic analysis confirmed the diagnosis of Pendred syndrome as a mutation in the <i>Pds</i> gene was found. The patient was treated with potassium iodine orally. During follow-up there where no symptoms of
hyperthyroidism and the size of the goitre decreased.