Radioiodine (Radioactive Iodine) Therapy

Last updated date: 06-Mar-2023

Originally Written in English

Radioiodine (Radioactive Iodine) Therapy

Radioiodine (Radioactive Iodine) Therapy


Radioactive iodine therapy is used to treat hyperfunctioning thyroid disease and thyroid cancer. It is categorized as radioactive nuclear medicine, and it was originally produced in 1941. The FDA authorized it for therapeutic use in 1971.

Its action destroys thyroid tissue permanently by producing two types of radiation, gamma and beta rays. Gamma radiation effects are more effective for diagnosis, but beta radiation effects are more beneficial for treatment. Its efficacy is dependent on iodine absorption from thyroid tissue and is ineffective in people with hyperfunctioning illness who do not have iodine uptake.

It is appropriate in patients with a high surgical risk and a shorter life expectancy, as well as in individuals who have failed to achieve euthyroid status or who are unable to take oral anti-thyroid medications. In individuals with thyroid cancer, radioactive iodine therapy can be used as an adjuvant therapy to surgery and can be given four to six weeks after surgery.

Permanent hypothyroidism (or underactive thyroid, which occurs when the thyroid does not release enough hormones) is a known adverse effect of RAI therapy for hyperthyroidism. Fortunately, hypothyroidism is far easier to treat with hormone replacement medication than hyperthyroidism. This is a lifetime therapy that is safe, dependable, and affordable.

Temporary side effects of RAI may include: Neck tenderness and swelling, Nausea, Swollen salivary glands, Loss of taste or taste change, Dry mouth/insufficient salivary production, Dry eyes, Excessive tearing from the eyes.


Uses of Radioactive Iodine

Uses of Radioactive Iodine

  • Grave's disease.
  • Toxic adenoma.
  • Toxic multinodular goiter.
  • Non-toxic multinodular goiter.
  • Well-differentiated thyroid carcinoma.

The use of radioactive iodine for diagnostic purposes can distinguish between hyper- and hypo-functioning thyroid disorders. This distinction is made by monitoring radioactive iodine absorption in the thyroid after 24 hours.

Increased RAIU:

  • Grave's disease.
  • Toxic multinodular goiter.
  • Thyroid adenoma. 

Decreased RAIU: 

  • Subacute thyroiditis
  • Painless thyroiditis
  • Iodine-induced hyperthyroidism
  • Factitious hyperthyroidism


How does Radioactive Iodine treat hyperthyroidism?

Radioactive Iodine treatment

The thyroid gland, a butterfly-shaped gland at the lower front of your neck, produces hormones that govern your body's metabolism and other activities. Hyperthyroidism causes uneasiness and anxiety, quick heartbeat, missing or light menstrual cycles, sleep problems, hand tremors, and other issues by speeding up the body's functions.

Iodine is required by the thyroid gland to produce these hormones. The thyroid gland is the most effective at concentrating iodine. RAI cures hyperthyroidism by causing thyroid cells to be damaged or destroyed by radiation.

RAI is given orally in the form of capsules. Unless the dose is really high, which is rarely the case, you do not need to be hospitalized. After swallowing the tablet, you will be instructed to drink plenty of water in order to flush any remaining radioactive iodine from your system.

Most people require just one dosage until their hyperthyroidism resolves, which might take several weeks to months. If your symptoms persist after six months, you may require a second treatment.


How does Radioactive Iodine treat thyroid cancer?

thyroid cancer treatment

Large dosages of radioactive iodine are often used to treat the most prevalent kinds of thyroid cancer (papillary and follicular). (The RAI dosages are substantially greater than for hyperthyroidism therapy.) The therapy is frequently administered after the thyroid gland has been removed in order to eradicate any leftover thyroid tissue.

A radioactive iodine "tracer" dosage can also be used to monitor leftover thyroid tissue and/or cancer that has migrated to other regions of the body. These tests determine if iodine concentrations are high in locations with thyroid cancer and whether substantial quantities of RAI are required to eradicate tumor implants.


How Radioactive Iodine is administered?

Radioactive Iodine

Iodine-131 is available as:

  • Oral gelatine capsules
  • Oral drinking solution.
  • Intravenous injections.


Medications contraindicated before therapy

  • Antithyroid medication (propylthiouracil, methimazole).
  • Amiodarone.
  • Contrast agents.

Because iodine is a natural precursor for thyroid hormones, medications containing iodine can inhibit its absorption from the transporter of thyroid cells during radioactive iodine treatment. All patients should follow an iodine-free diet for seven days, or longer if being treated for thyroid cancer.

Although it is contraindicated, in select individuals with severe hyperfunctioning thyroid disease or heart illness, treatment with the antithyroid drug methimazole may be begun prior to radioactive iodine therapy. Transient thyrotoxicosis may occur quickly after radioactive iodine therapy as a result of stored triiodothyronine (T3) and thyroxine leaking (T4).

Thionomide treatment may reduce thyroid hormone storage and maintain a euthyroid state to prevent thyrotoxicosis consequences. Methimazole is chosen over propylthiouracil (PTU) because to its high failure rate. If a patient is taking ethionamide, it is recommended that they stop taking it three to five days before starting radioactive iodine therapy.


What are the side effects of Radioactive Iodine?

Permanent hypothyroidism (or underactive thyroid, which occurs when the thyroid does not release enough hormones) is a known adverse effect of RAI therapy for hyperthyroidism. Fortunately, hypothyroidism is far easier to treat with hormone replacement medication than hyperthyroidism. This is a lifetime therapy that is safe, dependable, and affordable.

Temporary side effects of RAI may include:

Early Complications:

  • Nausea.
  • Vomiting.
  • Chest Pain.
  • Pruritis.
  • Hives.
  • Anemia.
  • Leukopenia.
  • Thrombocytopenia.
  • Teratogenicity.
  • Bone marrow suppression.
  • Radiation thyroiditis.
  • Sialadenitis/xerostomia.
  • Gonadal damage/Infertility.
  • Dry eye.
  • Nasolacrimal duct obstruction.
  • Transient thyrotoxicosis.
  • Pulmonary fibrosis.
  • Brain edema.


Late Complications:

  • Bone marrow depression.
  • Leukemia.
  • Stomach Cancer.
  • Bladder Cancer.
  • Breast Cancer.
  • Pulmonary fibrosis.
  • Permanent bone marrow suppression.
  • Genetic effects.
  • Hypothyroidism.

To prevent exacerbations of preexisting ophthalmopathy, individuals with preexisting ophthalmopathy should be treated with oral prednisone medication. Treatment can begin a few days following RAI therapy and should last 1 to 3 months. Thyroid tissue destruction caused by radioactive iodine treatment can produce thyroid antigens, which can travel to TSH autoantibodies in the orbital, producing inflammatory and osmotic consequences. Because RAI induces irreversible loss of thyroid tissue, it may predispose people to persistent hypothyroidism. Patients may require thyroxine treatment for the rest of their lives.


Contraindications of Radioactive Iodine use

Radioactive Iodine Contraindications

Radioactive iodine therapy (RAI) is contraindicated in the following:

  • Pregnancy.
  • Breastfeeding.
  • Carcinoma with no iodine uptake.
  • Graves ophthalmopathy (moderate to severe).
  • Severe thyrotoxicosis.
  • Vomiting.
  • Diarrhea.

The radioactive material can cross the placenta and cause irreversible thyroid damage and mental impairment in the developing fetus. Contraception is strongly advised to females of reproductive age who are considering radioactive iodine therapy. Before beginning medication, a negative pregnancy test should be considered because pregnancy and nursing are essential contraindications.


Before your Radioactive Iodine treatment

Radioactive Iodine treatment

  • Discuss your treatment plan.
  • Your doctor will discuss your treatment plan with you.
  • Your treatment plan will follow these steps that will take place over a few days:
  1. On the first day, you’ll have blood tests. After those tests, you’ll see your doctor and get a thyrotropin alfa (Thyrogen) injection (shot) to help you get ready for your treatment. This injection will help any leftover thyroid tissue absorb the radioactive iodine.
  2. On the second day, you’ll get another thyrotropin alfa injection. Then you’ll get a small diagnostic dose of radioactive iodine in a pill. You won’t have to follow any precautions (safety measures) after getting this small diagnostic dose of radioactive iodine. After you take this pill, you’ll have a whole-body scan. This scan will show your doctor how the radioactive iodine is being taken up in your body.
  3. On the third day, you’ll have your full dose of radioactive iodine treatment. This is an outpatient procedure, so you won’t be admitted to the hospital.
  4. You’ll have another whole-body scan several days after your treatment. This helps your doctor see where the dose of radioactive iodine was taken up in your body.


  • Follow a low-iodine diet: You’ll need to follow a low-iodine diet for at least 1 week before you start treatment. A low-iodine diet will make your radioactive iodine therapy more effective. If you have too much iodine in your diet, it can stop the thyroid cells from taking up the radioactive iodine. Continue to follow this diet for 24 hours after your treatment is completed, or as instructed by your doctor. Read the resource for more information.


  • Pregnancy and radioactive iodine therapy: Don’t get pregnant or get your partner pregnant for at least 6 months after getting radioactive iodine therapy, or as long as your doctor tells you to. Use birth control after treatment for at least 6 months after getting this treatment. If you’re planning to have a child, talk with your doctor about your plans before your treatment.


  • Breastfeeding and radioactive iodine therapy: Radioactive iodine can collect in breast tissue with milk in it. To prevent having radioactive iodine collect in your breast after your treatment, you’ll need to stop breastfeeding or pumping breast milk at least 6 to 12 weeks before your treatment.You won’t be able to continue breastfeeding after your treatment because your breast milk can expose your baby to radiation. 


  • Contact your insurance company: Once your doctor has gone over your treatment plan, call your insurance company to find out if you need preauthorization (a decision that’s made by your health insurance company that this procedure is necessary) for any treatments and tests. 


  • Plan for transportation after treatment: Radioactive iodine gives off radiation. This means that after your treatment, you won’t be able to go home using public transportation such as buses, the subway, trains, or a plane. You can drive yourself home, have someone pick you up and take you home, or take a taxi or private car home. See our ‘Resources’ section for information about car services.


  • Make a plan for getting home before you come for your treatment.


What precautions should be taken before Radioactive Iodine therapy?

Radioactive Iodine therapy

  1. RAI treatment should not be used by pregnant or breastfeeding women. Pregnancy should be avoided for at least six to twelve months following RAI therapy for thyroid cancer. Breast feeding should be discontinued at least six weeks before RAI and not restarted.
  2. Be mindful of these general measures to avoid radioactive exposure to others in the days after your RAI therapy. Your healthcare practitioner will provide you exact advice on how many days you must adhere to these measures, which will be determined by the strength of your RAI treatment.
  3. Avoid prolonged, close physical contact with others, particularly children and pregnant women.
  4. For the first several days, keep at least 6 feet apart from people. Avoid going to public areas.
  5. Sleep on a separate bed by yourself (at least 6 feet away from another adult).
  6. Kitchen and cooking equipment, beds, towels, and personal goods should not be shared with others.
  7. Do separate dishwashing and laundry for the goods you use.
  8. Wash your hands frequently and take a shower on a regular basis.


Should I regularly monitored after Radioactive Iodine therapy?


Patients who have had RAI treatment will require ongoing monitoring and frequent checkups for the rest of their lives. Thyroid function tests should be performed every 4-6 weeks for the next six months, or until the patient reaches an euthyroid or hypothyroid condition. TSH levels can stay low for a lengthy period of time despite the patient being clinically euthyroid, hence free thyroxine levels should be checked periodically following therapy. TFT can be followed for six to twelve months after the therapeutic effect has been achieved. If treatment failure is suspected and the patient remains hyperthyroid six months after treatment, the clinician may reconsider RAI retreatment.

RAI may cause several toxic effects:

  • Radiation-induced toxicity.
  • Hypersensitivity reactions.
  • Radiation-induced thyroiditis.

Potassium iodide (KI) decreases radioactive iodine absorption in the thyroid and can be useful during toxicity. RAI is rapidly absorbed through the gastrointestinal system and spreads to thyroidal tissue via the circulation after administration. RAI is mostly excreted through the kidneys. Patients with renal impairment are more likely to have reduced clearance as well as higher levels of RAI and toxicity. Patients should be warned to take precautions following RAI therapy, as radiation can be dangerous to others around them. Clinical personnel must take special precautions to prevent contact and exposure with pregnant women and children.


What should I do after Radioactive Iodine treatment?

Radioactive Iodine treatment

1. Getting home:

You will not be allowed to return home utilizing public transportation, such as buses, subway systems, trains, or planes, following your treatment. You have the option of driving yourself, having someone pick you up and bring you home, or using a taxi or private automobile. If you're driving home from your appointment and another individual is in the car with you, sit as far away from them as possible.


2. Clearing the radioactive iodine from your body:

Some of the radioactive iodine will be absorbed by your thyroid cells, but some will remain. The majority of the excess radioactive iodine will exit your body through your urine, with minor quantities exiting through your saliva, perspiration, and bowel motions.


3. Follow these guidelines to help the radioactive iodine leave your body quickly:

  • Drink plenty of fluids. Drink at least 1 cup of low-iodine liquid every hour while awake, beginning immediately after your treatment. Continue doing so for 2 to 3 days following your therapy. You don't have to get up in the middle of the night to drink liquids.
  • Because your urine will be radioactive, urinate as much as possible to clear your bladder. Make an effort not to get pee outside of the toilet. Wear gloves and clean it up with an all-purpose cleaning disinfectant if you get pee outside of the toilet. If you regularly stand while peeing, you should sit for 2 days following your treatment unless your healthcare professional instructs you otherwise. This is done to avoid getting pee somewhere else than the toilet. Instead of retaining it in your bladder, try to urinate whenever you feel the desire.
  • Your bowel movements will also be radioactive. Go to the bathroom as much as you can so your bowel movements don’t stay in your colon.


4. Manage your diet:

  • You can restart your normal diet 24 hours after your treatment unless you’re given other instructions by your doctor.
  • Keep drinking lots of liquids for 2 to 3 days after your treatment, at least 1 cup per hour.
  • If you drink alcohol, drink no more than 1 or 2 drinks per day.


5. Medications:

If you were told to stop taking your thyroid medications, start taking them again the day after your treatment as instructed by your doctor.

Take all other prescribed medications starting the day after treatment as instructed by your doctor.


6. Travel:

For the first 24 hours after being discharged , do not travel by plane, train, metro, or bus. This is done to ensure that you are not in close touch with other individuals for extended periods of time. Even a brief subway ride might turn into a long one if the train becomes stalled or delayed.

Your doctor will provide you with a pocket card containing information on your therapy. The card explains that you had Nuclear Medicine therapy and that you may emit minor quantities of radiation for up to three months afterward. If you are stopped by security at a checkpoint, such as at an airport or outside a tunnel, show this card.

7. Going back to work:

The radiation safety physicist will tell you when you can go back to work. This is usually 1 to 2 days after your treatment depending on what kind of work you do, and how close you’ll be to other people.



Radioiodine (Radioactive Iodine) Therapy

Radioactive iodine therapy (RAI) is a nuclear agent that has been authorized by the FDA for the treatment of hyperfunctioning thyroid disease and thyroid cancer. The use of this medication should be managed by an interprofessional team that includes an endocrinologist, a primary care doctor, nurses, and pharmacists. 

Thorough follow-up and communication between the primary care physician and specialists are essential for monitoring free T4 and TSH levels to determine therapy success or problems. Nurses and other providers who work directly with patients should be aware with the clinical signs and symptoms of treatment consequences such as thyroid storm, ophthalmopathy, and temporary hypothyroidism. Patients suffering from thyroid-associated orbitopathy may require the services of an ophthalmologist.

During pregnancy, it is extremely encouraged to seek counseling and discontinue therapy. A negative pregnancy test should be examined prior to treatment, as radioactive iodine can easily penetrate the placenta and be absorbed by the fetus, causing permanent harm. If necessary, select patients should be taught on pre-treatment, and all patients should be counseled on iodine restriction prior to therapy. Patients should be given specific advice about radiation toxicity and how to prevent contact with family members, pregnant women, and children.

The interprofessional team should also educate patients on the side effects of therapy, as well as any early and late consequences that may occur, as well as the severity of the issues.

RAI may cause temporary adverse effects such as neck discomfort and swelling, nausea, swollen salivary glands, loss of taste or change in taste, dry mouth/insufficient salivary output, dry eyes, and excessive weeping from the eyes.