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Thyroid Scan

Results

A thyroid scan uses a radioactive tracer and a special camera to make a picture of the thyroid gland. The radioactive tracer used in this test is usually iodine or technetium. A thyroid scan is done to help find problems with the thyroid gland.

Thyroid scan
Normal:

A normal thyroid scan shows a small butterfly-shaped thyroid gland about 2 in. (5 cm) long and 2 in. (5 cm) wide with an even spread of radioactive tracer in the gland.

Abnormal:

An abnormal thyroid scan shows a thyroid gland that is smaller or larger than normal. It can also show areas in the thyroid gland where the activity is less than normal (cold nodules) or more than normal (hot nodules). Cold nodules may be related to thyroid cancer.

A whole-body scan will show whether iodine is in bone or other tissue (iodine uptake) after the thyroid gland has been removed for cancer. The whole-body scan can check to see if cancer has spread to other areas of the body.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Taking thyroid medicine.
  • Eating foods with iodine, such as shellfish, iodized salt, or kelp.
  • Having other tests using contrast materials in the past 4 weeks.

What To Think About

  • Blood tests may be done before a thyroid scan to measure the amount of thyroid hormones (TSH, T3, and T4) in your blood. For more information, see the topics Thyroid-Stimulating Hormone (TSH) and Thyroid Hormone Tests.
  • Cancer of the thyroid is usually treated with surgery. If the tumor is large, has spread outside the thyroid gland, or has recurred, it may then be treated with very high doses of radioactive iodine. After treating recurring thyroid cancer, a scan of the entire body can be done to see where the cancer has spread.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Matthew I. Kim, MD - Endocrinology
Last Revised May 31, 2011
1 | 2 | 3

WebMD Medical Reference from Healthwise

Last Updated: May 31, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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