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What is 'radioactive iodine therapy'?

Radioactive Iodine Therapy

Hossein Jadvar (Doctor) gives expert video advice on: How is radioactive iodine therapy used in treatment of thyroid cancer?; What are the benefits and risks of radioactive iodine therapy?; Are there limitations to radioactive iodine therapy? and more...

What is 'radioactive iodine therapy'?

Well radioactive iodine therapy is the treatment of two major disorders of the thyroid gland and that is hyperthyroidism, for example, people with Graves' disease when their thyroid is hyper functioning or for treatment of thyroid cancer. So those are the two major areas that radio iodine is used for treatment.

What is the 'thyroid'?

The thyroid is a very, very important gland in our body, located in the low, what we call anterior, neck, in the front of the lower aspect of the neck. It is pivotal in the normal metabolism of the body. In fact, so important, that it develops during embryogenesis when we are in the womb. It is required to be functioning normally at some point when it's developed, for the human embryo to develop normally; mentally and physically. It's a very, very important gland that is simply involved in a variety of metabolic pathways in the body.

What is 'hyperthyroidism'?

‘Hyperthyroidism' is when the thyroid gland is hyper functioning - it's functioning too much. In other words, it's releasing the thyroid hormone, which is its product, too much into the bloodstream. Therefore, that can cause a number of problems in the metabolic pathways in the body, and there are certain signs and symptoms that are associated with that. Sometimes their thyroid gland can also be enlarged and you can actually feel it or see it, even in the anterior low aspect of the neck. These are all, again, pointing towards a hyper functioning thyroid gland.

How is radioactive iodine therapy used in treatment of thyroid cancer?

Patients who have thyroid cancer are usually treated surgically initially, by removal normally of the entire thyroid gland. That is called a total thyroidectomy. Then after that, the patient is usually treated with what we call appellation dose, radio iodine treatment and this is done sometime shortly after the surgery is finished, maybe a week or two after the surgery is done. The reason for that is to basically kill all the residual thyroid tissue that is left behind by the surgeon in the niche. At the same time it can show us if there are other sites, distance sites or local sites, in the body that the thyroid cancer has already metastasized. Then, after the treatment, the patient comes back to the nuclear medicine clinic in about 6 months, or sometimes a year depending upon their referring physician and their clinical condition, to see if there is evidence for recurrence of thyroid cancer that can be signalled by following or marking their blood which is called thyrogloblaring. Thyrogloblaring is produced by the thyroid tissue, so if in a patient that does not have a thyroid, after its resection shows that the thyroglobarling in their blood is going up, we know that there is thyroid tissue somewhere and therefore that prompts the patients for another radio iodine diagnostic scan. This is a low dose scan to see where the thyrogloblaring is coming from, and depending on what is seen on that survey, if there is for example evidence of an extetic disease, the patient is scheduled for a much larger dose of radio iodine treatment, and the amount of dose depends on how extensive the disease is.

What does the equipment used in radioactive iodine therapy look like?

The equipment that is used for a radio iodine scan is basically the same as the one that is used for general nuclear medicine, and nuclear cardiology. These are either planar or single photon emission computer tomographer spec systems, which have camera heads which collect gamma rays to form an image by the computer.

How does radioactive iodine therapy work?

The thyroid gland uses iodine, as it's an important constituent for making thyroid hormone, which is it's product. By giving radioiodine, we are replacing what iodine the thyroid gland would have taken up with this radioactive iodine. The radioactive iodine kills the thyroid cells, and by doing that we diminish the number of the active thyroid cells. In that way, we diminish the amount of product that is produced by the thyroid gland. Therefore, that's how we treat the hyper functioning thyroid - by declining the amount of thyroid hormone that is being produced.

What will I experience during radioactive iodine therapy?

There is really no specific sensation associated with radioiodine treatment, either for hyperthyroidism or for thyroid cancer. It has a very good record over the past decades of use of this procedure. However, the higher the dose the radioiodine is, for example when you use it for treatment of thyroid cancer, the patient initially may feel some of what we call stomach upset or discomfort. Therefore we ask them not to eat for two or three hours just so that they don't have a vomiting experience with bringing up the radioiodine which is actually administered orally to the patient. In patients who are hyperthyroid and are being treated with radioiodine treatment, in a very, very small percentage of them, they may develop what's called a thyrotoxicosis. That is when cells that are killed in the thyroid gland suddenly release a large amount of thyroid hormone that was within them. That large amount of hormones can have consequences, metabolic consequences, which we call thyrotoxicosis, which is like somebody having very high heart rates, with sweating, and fever even. But that occurs very seldomly, and can be actually, if it's expected in a specific clinical situation, can be prevented by giving appropriate treatment, other treatment beforehand, before the radioiodine is given or even when this develops, if it develops. So for the most part there is really no specific sensations or pain of any sort, but I wanted to mention these two things that some people may experience.

What are the benefits and risks of radioactive iodine therapy?

The benefits of radioiodine treatment, either for hyperthyroidism and for thyroid cancer is tremendous. It has a very good record over the past several decades of treating appropriately patients with these two very important disorders. Today it still continues to be a common procedure performed in nuclear medicine for treatment. The risks are really associated with the radioactivity. In this case, we usually give a somewhat higher dose, called a radiation dose, especially if they're treating patients with thyroid cancer which may receive a much larger dose than usual we give in general nuclear medicine for diagnostic purposes. But that also has to be taken in the context of the fact that the patient has cancer already and that we're trying to cure or treat it. The remote possibility of development of a new cancer because of radioactivity which is small, continues to be small, should be taken into this context, as this is an important and effective treatment for a patient with thyroid cancer.

Are there alternatives to radioactive iodine therapy for hyperthyroidism?

The basic alternatives for hyperthyroidism treatment to radio iodine is surgery and drugs. With surgery, basically, the entire or part of the thyroid gland is removed to diminish the functioning number of cells that produce thyroid hormone. There are also drugs available that the patient can take to interfere with the function of the thyroid or the effectiveness of the thyroid hormone that is available in the bloodstream, and they work effectively in many patients. However, if the hyperthyroidism is resistant to these drugs, or the patient is non-compliant in some sense with the drug treatment, then radio iodine therapy is very effective therapy for hyperthyroidism.

Are there limitations to radioactive iodine therapy?

You don't give the radioactive iodine therapy usually to pregnant patients, because as I mentioned before, that radio iodine is going to interfere with the normal development of the thyroid gland in the embryo. That can have very bad consequences in the development of the embryo, so we always, if the patient is female and child bearing age, we'll always ask them if they are pregnant, or whether they're planning to become pregnant soon . Therefore we don't give the radio iodine to patients who are pregnant. And that's, I would say, the major restriction that is used in radio iodine therapy.