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Radioactive iodine uptake (RAIU) is a test of thyroid function. It measures how much radioactive iodine is taken up by the thyroid gland in a given time period.
See also:Thyroid scan
Alternative NamesIodine uptake test; RAIU
How the test is performedYou are asked to swallow a liquid or capsule containing radioactive iodine.
After a certain period of time (usually 6 and 24 hours later), you must return to the testing center so that the amount of radioactivity in the thyroid gland can be measured. This is done using a device called a gamma probe.
The probe is placed over your thyroid gland along the outside of your neck. You will be asked to lie on a table while the scanner moves over your neck.
The scan takes about 30 minutes.
How to prepare for the testDo not eat for 8 hours before the test.
Your health care provider will instruct you, if necessary, to stop taking drugs that may interfere with the test.
Drugs that increase results include:
- Barbiturates
- Estrogen
- Lithium
- Phenothiazines
- Thyroid stimulating hormone
Drugs that decrease results include:
- ACTH
- Antihistamines
- Antithyroid drugs
- Corticosteroids
- Lugol's solution
- Nitrates
- Saturated solution of potassium iodide
- Thyroid drugs
- Tolbutamide
Tell your doctor if you have any of these factors:
- Diarrhea (may decrease absorption of the radioactive iodine)
- Recent x-ray test using iodine-based contrast (within the past 2 weeks)
- Too little or too much iodine in your diet
There is no discomfort. You can eat beginning about 1 - 2 hours after swallowing the radioactive iodine. You can go back to a normal diet when the test is finished.
Why the test is performedThis test is done to evaluate thyroid function. It is often done when blood tests of thyroid function (such as T3 or T4) show abnormal results.
Normal Values- 6 hours: 3 - 16%
- 24 hours: 8 - 25%
Note: Some laboratories only measure at 24 hours. Values may vary depending on the amount of iodine in your diet. Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results meanIncreased levels may be due to:
Decreased levels may be due to:
- Hypothyroidism
- Factitious hyperthyroidism
- Iodine overload
- Subacute thyroiditis
Additional conditions under which the test may be performed:
- Colloid nodular goiter
- Graves disease
- Painless (silent) thyroiditis
- Toxic nodular goiter
The amount of radioactivity is very small, and there have been no documented side effects. The amount of iodine used is less than the amount of iodine in a normal diet. However, as with any radiation exposure, this test is not recommended for women who are pregnant or breastfeeding.
People with a history of allergy to dietary iodine or shellfish may not be able to have this test. A history of allergy to iodine (contrast dye) does not necessaily mean you can't have this test. Talk to your health care provider.
Special considerationsThe radioactive iodine leaves your body through your urine. You may need to take special precautions, such as flushing twice after urinating, for 24 - 48 hours after the test. Ask your health care provider or the radiology/nuclear medicine employee performing the scan.
ReferencesAACE Thyroid Task Force. American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of hyperthyroidism and hypothyroidism. Endocr Pract. 2002;8(6):457-469.
Ladenson P, Kim M. Thyroid. In: Goldman L and Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007:chap 244.
Larsen PR, Davies TF, Schlumberger MJ, Hay ID. Thyroid Physiology and Diagnostic Evaluation of Patients with Thyroid Disorders. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 10.
What else can I help you with?
What can iodine tablets do against radiation?
Iodine tablets are taken by individuals who have just been or are being exposed to radioactive materials that include radioactive iodine. In nuclear fission reactors, uranium (or sometimes plutonium) fission to create energy. When these fuel atoms split (fission), there are a number of fission products that can result, including a radioactive isotope of iodine. In a reactor accident that includes a meltdown and the release of radioactive fission products into the environment, radioactive iodine can be present. By taking iodine tablets, an individual who is exposed to radioactive iodine that was released in a nuclear reactor accident can avoid having his body absorb this radioactive material. Taking iodine tablets keeps iodine levels in the body high, and the thyroid gland, which absorbs iodine, high. This effectively prevents radioactive iodine from being absorbed and taken up by the thyroid. As absorbing radioactive iodine can lead to thyroid cancer, taking iodine tablets is a good shield against uptake of the radioactive isotope.
Which compounds can be administered to reduce the absorption of radiation that targets the thyroid?
Potassium iodide (KI) can be administered to reduce the absorption of radioactive iodine by the thyroid. This helps protect the thyroid gland from radiation damage by saturating it with stable iodine, reducing its uptake of radioactive iodine. It is important to follow guidance from healthcare professionals on the appropriate dosage and timing of administration during a radiation emergency.
What does uptake mean in a bone scan?
The term uptake, when used in connection with the imaging method called a bone scan, refers to the amount of radioactive material that is taken in (taken up - uptake) by the bones to facilitate the imaging. To image bones this way, a radioactive chemical that "looks" like stuff that bones want to facilitate their health is injected into a patient. The bones see this material and start to collect it, and they end up gathering about half of it up (ball park figure). This causes the bones to "glow" with the emissions of the decaying radioactive material used in the procedure. An imaging system with a camera sensitive to the gamma rays is used to "look" at the bones and an image results. The uptake of the tracer will be determined by how fast the metabolism of the bone is working. Faster metabolism will mean more uptake. Cancer, infection and a few other things cause a lot of uptake, and that is what makes them visible. They stand out as "hot spots" on the image. The body metabolizes and dumps the radioactive material through the kidneys and urinary tract. You don't get any more radiation than a conventional X-ray gives you - probably quite a bit less. The tracer, commonly 99mTc-Medronate (MDP), is a phosphate-based compound with technetium hooked in so the material will "glow" in the gamma ray spectrum and can be seen with equipment set up to look for electromagnetic radiation in those energy ranges. The nuclear medicine technologist can probably answer more questions for you, as can your physician.
Describe one way that radioactive isotopes have been used in agriculture?
Radioactive isotopes have been used in agriculture to measure uptake of nutrients by plants. For example, radioactive phosphorus can be used to track the movement of phosphorus in soil and its absorption by plants, providing valuable insights into nutrient cycling and plant nutrition.
Does chromium assists in Potassium uptake?
Chromium does not directly assist in potassium uptake in plants. Potassium uptake is primarily facilitated by specific transport mechanisms in plant roots. Chromium, on the other hand, can affect plant growth and development but is not a key player in potassium uptake.
What does the medical abbreviation RAIU mean?
Radioactive Iodine Uptake
What department would perform a thyroid uptake?
Radiology, using radioactive Iodine, which must be sent in lead containers to protect others from exposure.
Which of the following compounds can be administered to reduce the absorption of radiation that targets the thyroid?
Potassium iodide can be administered to reduce the absorption of radiation that targets the thyroid. It works by saturating the thyroid with non-radioactive iodine, thereby reducing the uptake of radioactive iodine.
What is the medical term for nuclear medicine test that measures thyroid function is?
The thyroid scan and a radioactive iodine uptake test (RAIU), also known as a thyroid uptake, are types of nuclear medicine imaging.
What can iodine tablets do against radiation?
Iodine tablets are taken by individuals who have just been or are being exposed to radioactive materials that include radioactive iodine. In nuclear fission reactors, uranium (or sometimes plutonium) fission to create energy. When these fuel atoms split (fission), there are a number of fission products that can result, including a radioactive isotope of iodine. In a reactor accident that includes a meltdown and the release of radioactive fission products into the environment, radioactive iodine can be present. By taking iodine tablets, an individual who is exposed to radioactive iodine that was released in a nuclear reactor accident can avoid having his body absorb this radioactive material. Taking iodine tablets keeps iodine levels in the body high, and the thyroid gland, which absorbs iodine, high. This effectively prevents radioactive iodine from being absorbed and taken up by the thyroid. As absorbing radioactive iodine can lead to thyroid cancer, taking iodine tablets is a good shield against uptake of the radioactive isotope.
Which compounds can be administered to reduce the absorption of radiation that targets the thyroid?
Potassium iodide (KI) can be administered to reduce the absorption of radioactive iodine by the thyroid. This helps protect the thyroid gland from radiation damage by saturating it with stable iodine, reducing its uptake of radioactive iodine. It is important to follow guidance from healthcare professionals on the appropriate dosage and timing of administration during a radiation emergency.
What does potassium iodide do for you in a nuclear accident?
A nuclear event, such as an accident or war, is likely to produce a lot of radioactive iodine. The thyroid gland concentrates iodine, so any iodine that gets into a person's body is likely to end up there. The potassium iodide tablets provide more iodine than the thyroid can use, so the radioactive iodine is not so likely to be retained in the body. So the potassium iodide reduces exposure to radioactivity. It protects only the thyroid, and it only protects that against radioactive iodine, but it is better than nothing.
How iodine is used in both the diagnosis and treatment of thyroid disease?
Tc99m and I131 arent used in thyroid uptake and scan. Specically I123 is used to evaluate thyroid uptake and is also used to perform a scan mostly in addition to a pinhole collimator. Tc99m can be used just for the purpose of size and shape of thyroid but ultrasound is more specific for that and does not introduce a dose of radiation to the patient.
What is the gland doctors image with iodine-131?
The thyroid gland is often imaged using a salt of iodine-131 as this gland has a high uptake of iodine.
What is a thyroid uptake probe?
It is the instrument used in nuclear medicine to evaluate the functional status of thyroid. it has sodium iodide crystals and other electronic systems which will help to find out the radiations comming out from the patient after administration of radioactive Iodine 131.
How can you find metastatic papillary thyroid cancer with non-avid iodine uptake?
One of the best ways is with FDG-18 PET scans. This is because non-iodine avid disease is often metabolically super-active and concentrates the radioactive glucose rapidly. This then "lights up " on the PET scan.
What happens when Iodine-131 is overdosed by being injested instead of by being injected?
When iodine-131 is ingested, it gets absorbed in the body and concentrates in the thyroid gland, where it emits radiation. An overdose can lead to acute radiation sickness, damage to the thyroid gland, and an increased risk of developing thyroid cancer. Treatment may involve administering medications to block the uptake of radioactive iodine and monitoring thyroid function closely.
