Thyroid Uptake and Scan

THYROID UPTAKE AND SCAN

This test is used to determine the cause of hyperthyroidism. Because administration of very small doses of radioactive iodine is involved, women of reproductive potential must have a negative pregnancy test before the test can be performed. The doses of radioactive iodine involved in this test are very low, and do not pose a risk to the patient or individuals they come in contact with.

If you need to cancel your test, it is critical that you notify the office at least 24 hours prior to your scheduled test to avoid being charged for the radioactive iodine capsule that is needed for the test. To cancel a test, contact Linda, our nuclear medicine technician at (702) 499-7671.

Procedure

This test is only offered in the Henderson office. The patient is administered a capsule of radioactive iodine orally. They are asked to return at 4 and 24 hours for thyroid uptake measurements to be performed. We use a device like a Geiger counter to measure the percentage of the administered does of radioactive iodine that has been trapped in the thyroid gland at 4 and 24 hours after dosing. After the 24-hour uptake is measured, we take an image of the thyroid gland, called a scan. Iodine trapped in the thyroid will cause a dark spot to appear on a x-ray film, and can provide information about what parts of the thyroid gland are taking up the radioactive iodine.

Results

Graves Disease: the uptake values will be determined at 4 and 24 hours and the scan will show the entire gland to light up. The gland in Graves Disease is usually enlarged.

Hot Nodule (Plummer’s Disease): The uptake is usually elevated, but may be normal. The scan shows a nodule that lights up with the surrounding parts of the gland being inactive.

Subacute Thyroiditis: The uptakes are very low and the scan shows little radioactive iodine labeling of the thyroid gland. A virus or inflammatory reaction involving the thyroid gland typically causes this condition. It usually resolves without therapy.

Toxic Multinodular: The findings are essentially the same as seen with a hot nodule, except multiple nodules are present.