[The thyroxine hyperthyroidism (author's transl)].

24 of all patients observed between 1974 and 1976 suffering from thyrotoxicosis were found to have increased blood thyroxine (T4) levels without increased triiodothyronine ones. T4 hyperthyroidisms represented 3.5% of all hyperthyroidisms observed; they were in relation with Grave's disease (18 patients) or toxic nodular (6 patients); clinical pictures were quite usual; old age, severe illnesses, amiodarone and corticoids treatments, iodine excess, were sometimes being incriminated, but often no particular cause could be found. Preferential T4 secretion or impaired peripheral T4 conversion are two possible mechanisms of T4 hyperthyroidism.