The two studies will be carried out successively on the same patient population. The 131I uptake will be carried out first followed by the I therapy itself. The patients are compared with a placebo-treated control group going through the same course of treatment, but the 131I dosis will be 100 Gy (standard treatment). After the 131I therapy, all patients are followed during one year with a regular ultrasound scan of the thyroid gland and control of the metabolic status. The patient satisfaction is monitored by the use of a visual-analogue-scale.