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
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.
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
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.
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.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Matthew I. Kim, MD - Endocrinology|
|Last Revised||May 31, 2011|