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Can The Radioactive Iodine Uptake Test Confirm the Presence Of Graves Disease?

Many people with Graves’ Disease have received the radioactive iodine uptake test.  This test involves the person swallowing a small dosage of radioactive iodine.  The thyroid gland in turn will absorb the radioactive iodine, and this is then evaluated after six hours, and then once again after 24 hours.

Many endocrinologists use the radioactive iodine uptake test to come up with their diagnosis of Graves’ Disease.  However, it’s important to understand that this test does not conclude that someone has this autoimmune hyperthyroid condition.  If the results of the uptake test are high then this shows that the thyroid gland is secreting an excessive amount of thyroid hormone, and in many instances the person with a high uptake test will have Graves’ Disease.  This test can also determine the presence of hot and cold nodules, which can give the doctor an idea as to whether they are benign or malignant.

But while the radioactive iodine uptake test can be helpful, the only surefire method to confirm that someone has Graves’ Disease is by having positive TSH receptor antibodies.  TSI antibodies are the primary type, as if someone has these antibodies, then this 100% confirms that they have Graves’ Disease.  However, these antibodies can fluctuate, and as a result, about 20 to 25% of the time these antibodies are negative in people who have Graves’ Disease.  In other words, just because someone tests negative for these antibodies doesn’t mean they don’t have Graves’ Disease.

When Should Someone Obtain The RAI Uptake Test?

I get this question asked a lot, as people are concerned about receiving even small dosages of radioactive iodine, and so if someone has a low TSH and/or high Free T3 and Free T4 levels, they want to know if they should obtain this test.  I of course can’t tell them what they should do, but in my opinion this test is frequently unnecessary.  If someone tests positive for TSI antibodies, then in my opinion there really isn’t any reason to obtain the radioactive iodine uptake test.  Sure, it also can detect the presence of thyroid nodules, but so can an ultrasound.  And a fine needle aspiration is necessary to confirm whether any nodules are malignant, as a radioactive iodine uptake test won’t give this information.

But what if someone has negative TSI antibodies?  Well, if someone tests negative for TSI antibodies, then perhaps it makes a little more sense to obtain a radioactive iodine uptake test.  I personally would rather have the person wait a couple of months and get the TSI retested again, and then if the test is still negative I would be more open to them getting the uptake test .  But then again, what it really comes down to is whether or not a positive or negative uptake test will make a difference in your treatment plan.

For example, if you plan on taking the conventional route, if you have a low TSH and/or high thyroid hormone levels, usually the recommendations will be either antithyroid medication, or radioactive iodine treatment, regardless of what the radioactive iodine uptake test shows.  Now perhaps some endocrinologists will be more conservative and recommend antithyroid drugs instead of RAI if someone has positive thyroid blood tests, but has a negative radioactive iodine uptake test.   If this is the case then you might decide it’s worth getting the test.  So this might be something to discuss with your endocrinologist, as you probably will want to find out exactly why he or she is doing this test, and how a positive or negative result will affect his or her recommendations.

Are There Risks Of Receiving The Radioactive Iodine Uptake Test?

I honestly don’t know whether there are long term risks of receiving this test.  Even though this test uses a small dosage of radioactive iodine, and doesn’t obliterate the thyroid gland like RAI does, this doesn’t mean that it’s completely harmless.  I’d be hesitant to take anything with the word “radioactive” in it unless if it was absolutely necessary.  Of course any endocrinologist who recommends this test will tell you it’s safe, and most probably believe this to be the case.  But I’d still be cautious about receiving this test, especially if the TSI antibodies came out positive.  This once again will confirm that you have Graves’ Disease, and if you’re concerned about thyroid nodules then you can always get an ultrasound.

In summary, the radioactive iodine uptake test will not confirm the presence or absence of Graves’ Disease.  The only test that will do this is the test for thyroid antibodies.  And if this test is positive, then there probably isn’t a good reason to receive this test.  And even if it’s negative you still want to question your endocrinologist and find out what approach he or she would take if the test were to come back positive or negative.