Long-term follow-up studies on Iodine-131 treatment of hyperthyroid graves’ disease based on the measurement of thyroid volume by ultrasonography

In the present series of studies, the long-term (four year) effect of 80 Gy of131I treatment was evaluated in patients with hyperthyroid Graves’ disease whose thyroid volumes have been accurately estimated with a high resolution ultrasound scanner. One year after131I treatment, 23.1 % (3 out of 13 patients) remained hyperthyroid, 69.2% (9 out of 13) became euthyroid, and 7.7% (1 out of 13) were in a hypothyroid state. Since three patients in a hyperthyroid state one year after treatment were subsequently treated with either antithyroid drugs or additional131I treatment, the remaining ten patients (9 euthyroid and 1 hypothyroid patients) have been followed up for three more years. Two patients developed a hypothyroid state three years after treatment and one patient four years after treatment. Overall, 60% (6 out of 10 patients) were in a euthyroid state and 40% (4 out of 10) in a hypothyroid state, four years after 80 Gy131I treatment. There was no significant difference between eu- and hypothyroid groups in the sex ratio, age, radiation dose, therapeutic dose, thyroid gland volume, 24-hr131I uptake, the effective half-life of131I in the thyroid or the duration of hyperthyroidism.