Radioactive Iodine Uptake

The radioactive iodine uptake (RAIU) test is used to analyze the functioning of the thyroid gland. The thyroid gland, as we all know, produces the hormones T4 and T3, that help in regulating the rate of metabolism and also affects the functioning of many systems in our body. Iodine is an important component for the synthesis of these hormones. Hence, this test can determine whether the thyroid is working properly or not.

What is it?
As the name suggests, radioactive iodine uptake test uses the tracer iodine. The test is done to determine the causes of hyperthyroidism and to treat it effectively. The treatment of hyperthyroidism includes another procedure known as radioactive iodine therapy. For the test, the patient is asked to take liquid or a capsule containing radioactive iodine (¹³¹I sodium iodide). After 6 hours and 24 hours of this oral intake, the amount of radioactivity in the thyroid gland is measured with the help of gamma probe or a scintillation counter. The device is placed outside the neck region to take a scan of the gland. Generally, the uptake is between 15 to 25% within the 6 to 24 hours duration of the ingestion. The results may vary depending upon the diet of the patient and the amount of iodine already present in the system. Low uptake of the radioactive iodine suggests thyroiditis, high uptake suggests Grave's disease and an uneven uptake points towards the presence of thyroid nodules in the gland. There are no side effects of this test that have been reported. Nonetheless, due to the use of radioactive substance and gamma radiation exposure, this test is not advocated for pregnant women or those that are breastfeeding. There are a few precautions and dietary control that needs to be done while undergoing this test. They are mentioned below.

Precautions
The radioactive iodine uptake test call for certain precautions to be observed before the test so as to not affect the test results. These are:

• You are not to eat anything for 8 hours before the test.
• If you take any medications that affect the thyroid activity or the medicines such as cough syrups, kelp, certain heart medicine and multivitamins, you must inform your doctor beforehand.
• Inform if you are allergic to iodine. Although, the iodine used for the test is in minute quantities. Also inform about the general allergies that you have.
• If you had taken any other radioactivity tests within the last 2-3 weeks, it may affect the radioactive iodine test results.
• As mentioned earlier, do not undergo this test if you are pregnant or breastfeeding.

There is no fixed diet recommended before and after this test. But you may be asked to not eat any food containing high doses of iodine for sometime before the test and possibly, even after. The foods may include seafood or dairy products. You may also be prescribed a low iodine diet before the test.

Benefits and Risks
The benefit of this test is that the result is unique and cannot be obtained by other imaging procedures. It is less expensive and yet gives precise information. The test also helps to determine the next course of action to be taken in terms of treatments.

There are no potential risks involved in the test. Some may have allergic reactions due to iodine. There are no long term health effects due to low exposure of radioactive substance as well as gamma rays. There are also, no diet restrictions after the test and you may resume your normal diet after 2 hours of undergoing this test. The radioactive iodine leaves the body through urine. Hence, you may be required to flush the toilet twice within the nest 48 hours of the test. This diagnostic test is easy and does not pose any major health risks. On the contrary, it provides useful precise information about your thyroid gland. Keeping the precautions in mind, you may undergo this test in a better way.