A thyroid uptake and scan is a test that uses a radioactive substance and a scanning tool to evaluate the thyroid gland. The scanner picks up where and how much the radioactive substance was taken up by the thyroid. This helps determine the structure, location, size, and activity of the gland.
Reasons for Test
The scan may be ordered to:
- Determine the cause of an overactive thyroid— hyperthyroidism
- Test how well the thyroid is working
- Determine if a thyroid nodule is functioning (if it is making thyroid hormone)
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Thyroid scans are associated with very few risks. Tell your doctor if you:
- Have an allergy to medication or food, including iodine or shellfish
- Are (or might be) pregnant or breastfeeding—the test could expose the baby to radiation
- Take any medications on a regular basis—some can interfere with test results
- If you recently had any CT scans , cardiac catheterizations , or other imaging tests that use contrast dye
What to Expect
Prior to Test
- You may be asked to avoid certain food (containing iodine) or thyroid medication before the scan. Some can interfere with the results.
- Jewelry, dentures, and other metallic objects will be removed.
- You may be asked not to eat or drink anything after midnight.
- Your doctor may order some tests to measure the amount of thyroid hormone in your blood.
Description of Test
You will be given a radioactive substance by mouth. Once the substance has had time to collect in the thyroid, the scan begins. You will lie on your back with your head tilted back. You will be asked to lie very still at certain times. A scanner will take pictures of your thyroid from different angles. The camera is not an x-ray machine. It does not expose you to more radiation. You may need to return to the radiology department after 24 hours for additional pictures.
You will be able to leave after the test is done.
Because of the very low dose of radioactive substance used, the majority of the radioactive substance will leave your body in 1-2 days. You are not at risk for exposing other people to radiation. You can interact normally with them.
How Long Will It Take?
The scan itself takes about half an hour. The radioactive substance needs time to be absorbed before the scan. You may need to wait 4-6 hours if you take the substance by mouth.
Will It Hurt?
There is no pain associated with a thyroid scan. There may be times when you find it uncomfortable to lie still with your head tilted backward.
The pictures of the scan take about an hour to develop. A radiologist will examine them. Based on the results of the test, further studies or treatment will be recommended.
Call Your Doctor
Call your doctor if you experience any unusual pain or discomfort.
If you think you have an emergency, call for emergency medical services right away.
American Thyroid Association http://www.thyroid.org
Hormone Health Network—Endocrine Society http://www.hormone.org
Public Health Agency of Canada http://www.phac-aspc.gc.ca
The Thyroid Foundation of Canada http://www.thyroid.ca
Hyperthyroidism. Johns Hopkins University website. Available at: http://www.hopkinsmedicine.org/healthlibrary/conditions/adult/endocrinology/hyperthyroidism%5F85,P00408. Accessed November 28, 2017.
Hyperthyroidism and thyrotoxicosis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116479/Hyperthyroidism-and-other-causes-of-thyrotoxicosis . Accessed July 27, 2017. Accessed November 28, 2017.
Thyroid nodule. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115781/Thyroid-nodule . Updated December 11, 2015. Accessed November 28, 2017.
Thyroid nodules. American Thyroid Association website. Available at: http://www.thyroid.org/thyroid-nodules. Accessed November 28, 2017.
Thyroid scan and uptake. Radiological Society of North America Radiology Info website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=thyroiduptake. Updated February 1, 2017. Accessed November 28, 2017.
- Reviewer: EBSCO Medical Review Board James Cornell, MD
- Review Date: 11/2018
- Update Date: 12/14/2015