2022 年 4 巻 p. 5-9
In two patients who received potassium iodide after discontinuing thiamazole and propylthiouracil for Graves' disease due to adverse reactions, 99mTc thyroid scintigraphy performed prior to 131I administration after discontinuing potassium iodide and a 2-week low-iodine diet revealed RI accumulation in the thyroid gland was almost nonexistent. Blood free Thyroxine (fT4) were abnormally high and thyroid stimulating hormone (TSH) levels were abnormally low in both cases. Both patients were subsequently treated with 500 MBq of 131I. 24 hours later 131I scintigraphy showed 131I obvious accumulation in both thyroid lobes in both patients. Usually, the uptake functions of 131I are markedly higher than those of 99mTc and thyroid uptake of 99mTc is released within hours, while the 131I uptake increases over time. Discordances between 99mTc and 131I uptake may reflect these differences.
