INTRAVENOUS OR ORAL I-131 TREATMENT OF THYROTOXICOSIS AND THYROID-CANCER

The purpose of this study was to determine differences in I-131 biokinetics after oral or intravenous treatment of hyperthyroidism (0,81 GBq) or differentiated thyroid cancer (1,85 GBq) following thyroidectomy. 20 patients with differentiated carcinoma and 20 patients with hyperthyroidism were studied. In each group 10 patients were treated perorally and 10 patients intravenously. The integrated whole-body activities during therapy were significantly lower, by an average 23% (cancer) and 45% (hyperthyroidism) than after oral application. It is most likely that these differences between oral and intravenous application are due to the higher serum activity after intravenous therapy. It is concluded that a higher activity dose of I-131 must be given orally to achieve the same target dose as after intravenous application.