Follow-up after treatment for thyroid cancer

Thyroglobulin Back to top

Thyroglobulin is a protein that is normally made only by the healthy thyroid gland, but it can also be produced by papillary or follicular thyroid cancer cells. Levels of thyroglobulin can be detected in the blood.

When the thyroid gland has been removed and radioactive iodine given to destroy any remaining cancer cells, thyroglobulin should no longer be produced unless there are still cancer cells left in your body. This makes the thyroglobulin blood test a useful way of detecting any remaining papillary or follicular cancer cells. The blood test is often repeated every 6–12 months.

You may also have radioactive iodine scans (the same as the thyroid radioisotope scan|) from time to time, to check whether there are any thyroid cancer cells in your body.

Before a thyroglobulin blood test or a radioactive iodine scan you will need to stop taking your thyroid hormone replacement tablets. If you are taking thyroxine (T4), you will need to stop taking it 4–6 weeks before the scan. Triiodothyronine (T3) tablets will need to be stopped 2–3 weeks before. This is done so that the body will produce enough thyroid-stimulating hormone (TSH) to make the tests as accurate as possible. TSH makes any thyroid cells, or thyroid cancer cells, that may be left in your body produce thyroglobulin and absorb radioactive iodine.

Stopping the hormone replacement tablets will mean that your levels of thyroid hormones will get lower. As a result you will begin to develop the symptoms of hypothyroidism, such as depression, weight gain, forgetfulness, decreased concentration and tiredness|. This may affect your ability to drive or operate machinery. You can start taking your tablets again once the tests are finished. The symptoms should begin to reduce as the level of thyroid hormones in your bloodstream increase.

Recombinant human thyroid stimulating hormone (rhTSH) Back to top

It may be possible to be treated with recombinant human TSH (or rhTSH) to overcome the problems of stopping your hormone replacement treatment. This man-made drug (also known as thyrotropin alfa or Thyrogen®) is similar to the TSH produced in your body. If you are given rhTSH you do not need to stop taking your thyroid hormone replacement tablets, and will not develop the symptoms of hypothyroidism.

The drug rhTSH is given as an injection, usually into the muscle in your buttock. You will be given two injections, 24 hours apart. You can be given the radioactive iodine the next day if you are having a scan. The scan will then be done 48–72 hours later. The thyroglobulin blood test is done 72 hours after your second injection of rhTSH.

There are very few side effects to rhTSH. Some people feel sick (nausea|); are sick (vomit|); have headaches; or feel weak. rhTSH is not suitable for everyone, and your doctor can tell you if you are able to have this treatment.

Scanning Back to top

Sometimes it is possible for thyroglobulin to be detected in the blood after treatment for thyroid cancer. This suggests that there may still be some cancer cells, however thyroid cells may not be found when a radioactive iodine scan is done. In this situation, a PET/CT scan may be used to help detect any cells that may be there.

A small amount of a radioactive substance is injected in the same way as a standard PET scan|, and then the CT scan| takes a series of x-rays. The scanner combines the information from the two scans and allows your doctor to measure any changes in the activity of cells and to know exactly where in the body the changes are.