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Radioactive iodine uptake |
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| Definition: | A test of thyroid function that measures the amount of orally ingested radioactive iodine that accumulates in the thyroid gland (see also "thyroid scan").
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| Alternative Names: | Iodine uptake test; RAIU
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| How the test is performed: | RAIU is a type of nuclear test of the thyroid that measures how much radioactive iodine is taken up by the thyroid gland in a given time period. You are asked to ingest radioactive iodine (I-123 or I-131) in liquid or capsule form. After a time (usually 6 and 24-hours later) you must return to have the radioactivity measured. A probe (gamma probe) is placed over the thyroid gland in the neck to measure the amount of radioactivity in the thyroid gland. This amount of radioactivity is compared to the original dose of radioactivity and reported as a percent of the original dose.
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| How to prepare for the test: | Fast for 8 hours before the test.
Consult with the health care provider if you have a history of factors that may affect the test (see "special considerations"). The health care provider may restrict iodine and thyroid (or anti-thyroid) medications for 1 week before the test.
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| How the test will feel: | There is no discomfort. You can eat beginning about 1 to 2 hours after ingesting the radioactive iodine, and you can resume a normal diet when the test is finished. For the scanning, you are asked to lie on a table while the scanner is placed over the neck. The scan takes about 30 minutes.
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| Why the test is performed: | This test is performed to evaluate thyroid function, particularly when blood tests of thyroid function (for example, T3 or T4 levels) have abnormal results.
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Review Date: 2/27/2002
Reviewed By: Donna R. Cooper, M.D., M.P.H., Department of Medicine, Massachusetts General Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.
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The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2003 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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