TTA is usually performed with a radioiodine dose of 30 millicurie (mCi), administered after 2 injections of recombinant human thyrotropin TSH (rhTSH), the latter in order to induce radioiodine uptake by thyroid remnants. According to the Italian legislation the administration of such a dose of radioiodine must be followed by a 24 hours protected hospitalization. Clearly, this necessity implies a remarkable increase of the waiting list, due to the limited number of radiation-isolated beds available and, concerning GO patients, to the competition with patients with thyroid cancer. In contrast, a radioiodine dose of 15 mCi can be performed in out-patients without hospitalization and with much lower costs. Concerning GD patients, they usually have serum TSH-receptor stimulating antibodies that ay persist after thyroidectomy and that may increase radioiodine uptake along with rhTSH, possibly resulting in the need for a lower dose of radioiodine to ablate thyroid remnants. In order to investigate whether this is the case, the present study was designed in patients with GD. The study design was to include patients scheduled to radioiodine treatment with 30 or 15 mCi after administration of rhTSH, being the primary outcome the values of serum thyroglobulin at peak after administration of rhTSH 6 months after radioiodine, as a measure of the presence of residual thyroid tissue.