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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uptake [up´tāk]

absorption and incorporation of a substance by living tissue.

biologic uptake movement of hazardous substances from the environment into the tissues of plants or animals.

radioactive iodine uptake (radioiodine uptake) uptake of radioiodine from the blood by the thyroid gland; see radioiodine uptake test.

T3 resin uptake (triiodothyronine resin uptake) the uptake of radioactive triiodothyronine at binding sites on resin, contrasted to uptake at sites on thyroxine-binding globulin in the triiodothyronine resin uptake 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.