Thyroid Uptake and Scan

(Thyroid Scintiscan; Technetium Thyroid Scan)

by Julie J. Martin, MS

Definition

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 TOP

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)

Thyroid

Possible Complications TOP

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 TOP

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.

After Test TOP

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? TOP

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? TOP

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.

Results TOP

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 TOP

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.

RESOURCES:

American Thyroid Association
http://www.thyroid.org

Hormone Health Network—Endocrine Society
http://www.hormone.org

CANADIAN RESOURCES:

Public Health Agency of Canada
http://www.phac-aspc.gc.ca

The Thyroid Foundation of Canada
http://www.thyroid.ca

References:

Hyperthyroidism. Johns Hopkins University website. Available at:
...(Click grey area to select URL)
Accessed December 14, 2015.

Hyperthyroidism and thyrotoxicosis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.... Updated March 21, 2016. Accessed October 10, 2016.

Thyroid nodule. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115781/Thyroid-nodule. Updated December 11, 2015. Accessed October 10, 2016.

Thyroid nodules. American Thyroid Association website. Available at:
...(Click grey area to select URL)
Accessed December 14, 2015.

Thyroid scan and uptake. Radiological Society of North America Radiology Info website. Available at:
...(Click grey area to select URL)
Updated March 28, 2013. Accessed December 14, 2015.

Last reviewed December 2015 by Kim A. Carmichael, MD
Last Updated: 12/14/2015

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