Podcast - The Radioactive Iodine Uptake Test

EPISODE 16

Many people with hyperthyroidism are told to get the radioactive iodine uptake test by their endocrinologist.  But is this test really necessary?  In this episode Dr. Eric discusses whether those with hyperthyroidism should get this test done, and if there are any risks with getting it.

During this episode you’ll learn:

  • What is the radioactive iodine uptake test
  • Why many endocrinologists recommend the radioactive iodine uptake test to their hyperthyroid patients
  • When someone should get this test done
  • Why the radioactive iodine uptake test shouldn’t be used to detect hot or cold thyroid nodules

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Here is the transcript for this episode:

Welcome back to the Save My Thyroid podcast. This is Dr. Eric Osansky,and in this episode, I am going to talk about the radioactive iodine uptake test.

What is the radioactive iodine uptake test? This test involves a person swallowing a small dosage of radioactive iodine. The thyroid gland will in turn absorb the radioactive iodine. This is then evaluated after six hours, and once again after 24 hours. Many endocrinologists will use the radioactive iodine uptake test to come up with their diagnosis of Graves’ Disease. This test can also determine the presence of hot and cold thyroid nodules.

However, there are two other ways of diagnosing Graves’ Disease. My favorite way is by looking at the thyroid antibodies. Specifically, the thyroid stimulating immunoglobulins, TSI, which is a type of TSH receptor antibody. If these are elevated, this is pretty much diagnostic of Graves’ Disease. Also, if someone has hyperthyroidism combined with thyroid eye disease symptoms, then there is a really good chance that they have Graves’ Disease. Not just dryness, but bulging of the eyes along with hyperthyroidism. That can be diagnostic. Most of these people will have elevated antibodies. I wouldn’t rely on that…if someone has hyperthyroidism combined with thyroid eye disease symptoms, as I would still want to test the antibodies.

When should someone obtain the radioactive iodine uptake test? In my opinion, this test is frequently unnecessary. In fact, when I was seeing an endocrinologist before I was diagnosed with Graves’, she did not recommend the radioactive iodine uptake test. Her reasoning was at the time I didn’t have health insurance, and it was an expensive test, and she didn’t think it was necessary. It just made me wonder from that point on if this test was really necessary to do. Do some endocrinologists do it because it’s another way of making money? I’m not saying all endocrinologists do this, but it’s something to consider.

If someone has elevated TSI (thyroid stimulating immunoglobulins) or TSH receptor antibodies—TSI is a type of TSH receptor antibody—either one of these is fine. If they are elevated, this will confirm Graves’ Disease. Then you might wonder, well, the radioactive iodine uptake test will look for hot and cold thyroid nodules, which is true. But this won’t confirm or rule out a malignancy. In my opinion, I would say to get a thyroid ultrasound instead of a radioactive iodine uptake test. Of course, it’s up to you. It’s your decision. But that was my decision. Even though the endocrinologist didn’t recommend it, I probably wouldn’t have gotten it anyway. I did ask for a thyroid ultrasound.

Let’s discuss hot and cold nodules. About 80-85% of thyroid nodules show up as being cold on the uptake test. About 10% of these nodules are malignant. Hot nodules account for only 5% of nodules although the likelihood of these being malignant is less than 1%. You’re hoping to see a hot nodule, but you’re far more likely to see a cold nodule. 90% of these will be benign. Once again, the uptake test isn’t going to confirm this, so if it shows a hot or cold nodule, you want to look at other characteristics: if the nodule is larger in size, let’s say two centimeters or greater; if it’s solid; and if it has microcalcifications. If it has two or three of the characteristics I just mentioned—a larger nodule, solid, microcalcifications—then you might want to consider doing a biopsy. As I mentioned, the uptake test is not going to confirm or rule out a malignancy. Neither will an ultrasound. Either way, you might need to do some more diagnostic testing.

Perhaps you’re still on the fence about receiving this treatment. Maybe not. Maybe you’re convinced you are not going to get this. But if you are on the fence, if you have an upcoming endocrinologist appointment and you have this scheduled, or you think they might recommend this, just keep in mind that everything comes down to risk versus benefits.

I also need to mention that this is not the same as receiving radioactive iodine treatments. Most people listening to this probably know that, but I still wanted to make that clear. However, even a small dosage of radioactive iodine shouldn’t be taken lightly. What you need to ask yourself is will obtaining this test change the course of treatment? Usually, the answer is no. In most cases, with hyperthyroidism, the three treatment options will be antithyroid medication, radioactive iodine, or thyroid surgery. If you already did receive this test, don’t feel bad. Again, it’s not the same as receiving radioactive iodine treatment. It’s not the end of the world. But if you haven’t, it’s something to consider maybe not doing. I can’t tell you not to do it. That’s up to you. But I am putting together this presentation so you can make an informed decision.

Let’s go ahead and summarize this episode. Once again, the radioactive iodine uptake test involves a person swallowing a small dosage of radioactive iodine. Many endocrinologists will use this test to come up with a diagnosis of Graves’ Disease. However, if someone has an elevated TSI or TSH receptor antibody—again, TSI is a type of TRAB—elevated Graves’ Disease antibodies will confirm Graves’ Disease. While this test can detect hot and cold thyroid nodules, it won’t confirm or rule out a malignancy. Once again, this test usually won’t change the course of treatment.

I know this was a brief presentation. I just wanted to go over some basics so you could make an informed decision. Ultimately, it’s up to you if you want to get the radioactive iodine uptake test. If you already got this test, I wouldn’t stress over it. What’s done is done. Go ahead and move on. That’s it. Thanks again for tuning in. Hope you found this episode to be valuable. I look forward to catching you on the very next episode.