Radioactive iodine treatment of metastatic thyroid carcinoma with clinical thyrotoxicosis.

We present a case of well-differentiated follicular carcinoma of the thyroid with hyperfunctioning metastases and clinical thyrotoxicosis. The recommended I-131 treatment dose for patients with widespread bone metastases from thyroid carcinoma is 200 mCi. However, in a patient with hyperfunctioning metastatic tumor and increased radioiodine uptake, the treatment dose should be modified. Radiation dosimetry measurements performed on the patient in this study demonstrated that 132 mCi would be a safe therapeutic I-131 dose which would avoid injury to normal radiosensitive tissues. Consequently, she was given a 130-mCi therapeutic dose.