Routine Testing for Thyroid Cancer

When you go in for follow-up tests, a goal is to see if your thyroid cancer has redeveloped. One way this is done is to check for thyroid activity in your body. The two most common follow-up tests are thyroglobulin (Tg) tests and whole body scans (WBS). Both of these can indicate the presence of thyroid activity.

Tg testing

This is a test that measures the amount of thyroglobulin in your blood. If you have had your whole thyroid removed (total thyroidectomy), you should have little or no Tg in your blood, since thyroid cells are the only cells that make Tg. If your Tg level is higher than expected, it means that thyroid or thyroid cancer cells may exist somewhere in your body.

A whole body scan uses radioiodine (RAI) to check for thyroid cells. The amount of RAI used for a WBS is significantly smaller than that used for ablation, and fairly safe. About 2 days after you have taken a drink or a capsule containing the RAI, you will be scanned by a large X-ray. Any thyroid cells anywhere in your body should have taken up the RAI, and should show up as spots on the X-ray film.

Testing preparation

One of the most important preparations to make for a scan is a low-iodine diet, which you may need to observe for a couple of weeks before your scan. You should check with your doctor to see whether he or she has a specific diet or timeline for you to follow. You can also find some suggestions about foods that can make up this diet and foods that should be avoided in the Low-Iodine Diet section of this site.

Additionally, both Tg testing and WBS usually require that you have elevated levels of thyroid stimulating hormone (TSH) in your bloodstream to stimulate any remaining or reappearing thyroid cells. Currently, there are two ways to do this. One is to stop taking your thyroid hormones, which should make your body produce TSH and induce a condition called hypothyroidism. The other alternative is to continue taking your thyroid hormones, but supplement your body’s TSH.

Other tests

Especially if you have had a positive Tg test and/or WBS, your doctor may decide to have you take other tests to confirm or rule out a recurrence of thyroid cancer. These include: