Test Details & Preparation
Test details and preparation:
- A radioactive iodine uptake (RAIU) test uses a radioactive tracer which is radioactive iodine of I-131 or I-123 and a special camera to measure how much tracer the thyroid gland absorbs from the blood.
- The RAIU test often is done along with a thyroid scan, which shows if the tracer is evenly spread in the gland. This helps the doctor to know if the thyroid gland is working properly or not.
- The test can be done to know:
- Find the cause of an overactive thyroid gland (hyperthyroidism)
- Plan treatment for hyperthyroidism.
- Plan treatment for patients who have had thyroid cancer surgery.
- The test is done by giving the patient already mage radioactive capsule which is swallowed or a liquid injection 4 to 24 hours before the test.
- The patient should tell the doctor whether she is pregnant or breastfeeding, about major scans he/she has gone through such as CT-scan,X-ray 4 weeks before the test, any allergic reaction etc.
- The patient should stop taking any anti-thyroid medicine, medicine and supplements which contain iodine.
Results and Risks:
- If the amount of tracer taken by the thyroid gland is normal then the result is normal.
- If the amount taken is less or high then certain conditions of hyperthyroidism may be present.
- The cases are-
- A low uptake of tracer by the thyroid gland may mean that hyperthyroidism is caused by inflammation of the thyroid gland (thyroiditis), taking too much thyroid medicine, or another rare condition.
- A high uptake of tracer spread evenly in the thyroid gland may mean that hyperthyroidism is caused by conditions such as Graves' disease.
- Risk which poses through this test is that some tissues can be damaged due to radiation but it show no long term damage.