Thyroid Nuclear Medicine Tests

What Is It?

1. Thyroid Scan: This test produces an image of the thyroid gland. It is used to detect thyroid abnormalities such as enlargement, inflammation, or the presence of nodules. It can also help investigate the cause of an overactive thyroid.
2. Radioactive Iodine Uptake Test: This test is performed to assess the normal functioning of the thyroid and to determine why thyroid hormone levels may be elevated. It involves the use of a weakly radioactive substance (radionuclide).

What It’s Used For

• A thyroid scan is typically ordered when a physical examination or laboratory findings suggest thyroid enlargement or the presence of thyroid nodules.
• The radioactive iodine uptake test is often conducted alongside a thyroid scan to evaluate thyroid function, especially when laboratory tests indicate an overactive thyroid.

Preparation

• Inform your doctor if you are pregnant or breastfeeding, as radionuclides can harm a developing fetus or nursing baby.
• Avoid certain foods and medications that can interfere with the test results, including thyroid hormones and iodine-containing foods like shellfish.
• Notify your doctor about any vitamins or herbal supplements you are taking.
• Fasting might be required for several hours before the test, especially if you will receive a radioactive iodine pill.
• Consent forms may be required.
• Remove all jewelry and dentures before the scan.

How It’s Done

• Radionuclide is administered either through an intravenous injection or as a pill.
• The timing of the test depends on the type of radionuclide used and whether both a scan and uptake test are performed.
• After receiving the radionuclide and waiting for the appropriate time, a radioactivity detector is used to take images of your thyroid.
• The camera used does not expose you to radiation.

Follow-Up

• Most of the weakly radioactive substances used in these tests are eliminated from the body within a day or two.
• There is no risk of significant radiation exposure to others.
• The images are developed and examined by a radiologist, and the results are typically provided to your doctor within a day or two.

Risks

• The risks associated with a thyroid scan are minimal, with radiation exposure similar to that of a routine x-ray.
• The amount of radionuclide used is very small and unlikely to cause side effects or allergic reactions.

When to Call a Professional

• People usually need to contact their doctors only to discuss scan results.

If you have any further questions or need additional information, you can explore our course on How to Manage Thyroid Disorders.