[Radionuclide therapy of thyroid disease--radioactive iodine therapy]

Radioiodine, 131I, has been used for treatment of hyperthyroidism and metastases of well differentiated thyroid carcinoma since 1942. The use of 131I to treat hyperthyroidism and metastatic foci of thyroid cancer is one of the least invasive and most effective methods since the ionization produced by beta rays of 131I and it's high target-to-nontarget ratio are suitable. The feature of therapy with 131I on hyperthyroidism has a slow improvement of symptom, a high incidence of hypothyroidism, and an exact therapeutic effect. And, there is no significant difference between the patients with late-onset hypothyroidism and euthyroidism after 131I-therapy in the pretreatment factors, such as thyroid hormone levels, thyroid weight, 131I administration dose, and absorbed dose and also in the course of follow-up studies. On the treatment of metastases of thyroid cancer with 131I, it is very effective for the patients with fine or occult type of pulmonary metastases on chest XP, who are younger than 40 years old. On the other hand, the response to bone metastases of 131I therapy is limited to only a part of tumors and/or temporally in most cases though high grade of 131I accumulation is seen on scintigram. Both surgery and a curative dose of external irradiation should be combined with radioisotope therapy for the patients of bone metastases.