radioactive iodine uptake

radioactive iodine uptake (RAIU),

the absorption and incorporation by the thyroid of radioactive iodine (RAI), administered orally as a tracer dose in a test of thyroid function and as larger doses for the treatment of hyperthyroidism. The radioisotope ¹³¹I is rapidly absorbed in the stomach and concentrated in the thyroid. Normal findings are 4% to 12% absorbed in 2 hours, 6% to 15% absorbed in 6 hours, and 8% to 30% absorbed in 24 hours. Patients receiving a large therapeutic dose of RAI may require hospitalization for several days. See also radioactive iodine excretion test.

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radioactive iodine uptake

RAIU, thyroid scan, thyroid scintigraphy Nuclear medicine A method of assessing thyroid function, using radioactive iodine–eg, 131I or 123I; ↑ in hyperthyroidism, ectopic hormone production, iodine deficiency, and in response to thyroid hormone depletion; ↓ in hypothyroidism, after administration of exogenous thyroid hormone, in defects of hormone storage, after exposure to iodine overload Normal range 5-25%. See T3, T4, TSH.