The evaluation of radioiodine therapy for thyroid patients using a fixed-dose regime

Ninety-six patients with toxic diffuse goitre (Grave's disease) in whom rapid control of disease was necessary were treated with an "ablative" dose of 550 MBq of radioiodine (131I) with the intention of inducing hypothyroidism. Outcome was established in 93 cases (mean follow-up 37 months), 45 patients (48%) becoming hypothyroid, 30 (32%) remaining euthyroid and 18 (19%) with persistent thyrotoxicosis requiring further 131I therapy. It is thus apparent that a fixed dose of 550 MBq 131I cannot be considered ablative, with less than 50% of patients developing hypothyroidism.