Radioactive Iodine Treatment

What is Radioactive Iodine Treatment? How Does It Treat?


Theranostics is a recently developing field of the medicine. This approach takes body images using a tumor-specific agent to locate the tumor and its metastasis and their potential future locations and it also uses a specific agent with pre-determined therapeutic efficiency for the diseased tissue. This approach enables switching from traditional medicine to contemporary personalized medical procedures.

Administration of low-dose radioactive iodine (I-131 or I-123) to obtain images with high sensitivity and specificity of tumor tissues for diagnostic purposes combined with high-dose radioactive iodine (I-131) for specific and targeted treatment of these tumors is the oldest known example of theranostic practices in thyroid cancer.

Radioactive iodine treatment is a standard practice with proven effect on survival which has been frequently preferred for treatment of benign and malignant (cancer) diseases of thyroid since 1940s.

Thyroid tissue has a unique ability to collect all iodine from the bloodstream and store it in the gland. Similar to iodine, radioactive iodine accumulates in the thyroid gland and is stored in thyroid tissues. Differentiated thyroid cancers also have this characteristic even though they are less potent than healthy thyroid tissues.

Although majority of patients have a very high chance of recovery in differentiated thyroid cancers, the risk of relapse or recurrence may be up to 20-30% and relapse may occur even decades after the baseline treatment. Therefore, regular follow-up is necessary for the patients to figure out a relapse and the follow-up should be maintained in the rest of the patient’s life.


Who is Eligible For Radioactive Iodine Therapy?

Radioactive iodine (I-131 or radio-iodine treatment) is administered to patients with differentiated thyroid cancer upon request of the primary physician (who follows up the patient) for following reasons:

  • To clear out postoperative residual healthy thyroid tissue with radiation (ablation)
  • Treatment of a microscopic disease
  • Treatment of residual/recurrent or metastatic thyroid cancer.


Postoperative Radioactive Iodine Ablation

It implies radioactive iodine treatment that aims at elimination of residual thyroid cancer cells or residual healthy thyroid tissue several weeks after the surgical treatment. Moreover, ablation is also performed to eliminate thyroid cancer cells, which have already spread to other body parts. Destruction of healthy thyroid tissue residues will facilitate the ability to monitor potential relapse of the disease in the follow-up.


Treatment of Recurrent or Residual Differentiated Thyroid Cancer with Radioactive Iodine

Surgery is usually the first-line option if the cancer tissue is operable. Radioactive iodine treatment can be performed alone or in combination with surgery.


Is Radioactive Iodine Treatment Safe?

It is easy to perform this treatment and the radioactive iodine solution that is ingested by patients during the treatment has no distinctive taste or smell. Patients feel nothing during the treatment. Unlike other cancer treatments, this treatment does not cause hair loss.

Radioactive iodine treatment is clearly contraindicated for pregnant women. Nursing mothers have to stop breastfeeding. 

Radioactive iodine therapy can be used in hemodialysis patients.

Patients with iodine allergy are eligible for radioactive iodine treatment.

It is necessary for both male and female patients to use effective birth control methods with their partners and avoid pregnancy for at least 6 months following the radioactive iodine treatment. 

Potential side effects of radioactive iodine treatment and preventive measures are summarized below. However, our Nuclear Medicine physician will discuss this matter with you and s/he will also inform and guide you to make the treatment period as much comfortable as possible. Always remember that strict compliance with such advice will minimize the side effects.


RPotential Side Effects of Radioactive Iodine Treatment


Early Side Effects


Sensation of burn and tenderness in neck

It is related to volume of postoperative residual thyroid tissue. Medication treatment can be prescribed if you have such a complaint.

Inflammation of oral mucosa and associating small painful sores

This problem can be prevented in most cases by gently brushing the entire oral mucosa with a soft brush once every 3-4 hours at day time for 4-7 days. Repeating this once every 3 hours at night for the first 4 days following the treatment may be added to this procedure.

Nausea ( and vomiting in rare cases)

Preventive medication therapy can be started before the treatment.

Swelling and tenderness in salivary glands

– Good hydration- 2.5-3 liters of liquid (except for milk) per day for approximately 1 week- is necessary.

-Sugar-free chewing gum and minty candies etc. increase the flow rate of saliva. This should be started 2 hours after the treatment and it should be repeated once every 3 hours throughout the day time (or while patient is not sleeping) and during night for 4 days after the treatment.

Preventive medication therapy can be started before the treatment. .

Partial loss or change in sensation of taste

This condition is generally temporary; no particular precaution is necessary.

Decrease in tear production


Temporary decrease in white blood cell and platelet counts

This may occur following high-dose radioactive iodine treatment (150-200 mCi).  However, it is not expected in patients with normal blood counts and renal function tests before the treatment.

Late side effects


Fertility in men

Temporary decrease in fertility is likely. However, irreversible infertility may occur in patients who receive multiple high-dose radioactive iodine treatments. Sperm cryopreservation may be considered before the treatment in such circumstances. Well hydration and frequent voiding will be beneficial for all patients who receive this treatment to decrease dose exposure (which originates from the bladder) in testicles.

Fertility in women

Radioactive iodine treatment is not expected to impair female fertility or increase the risk of miscarriage. Good hydration and frequent voiding will be beneficial for all patients who receive this treatment to decrease dose exposure which originates from the bladder.

Dry mouth, change in sense of taste, formation of stone in salivary glands, dentine carries.

Oral hygiene requires attention.

Dryness and watering of eyes


Occurrence of a secondary cancer

This condition occurs very rarely (<1%) following high-dose radioactive iodine treatment. The reported cases generally consist of patients who are exposed to high doses in multiple treatments. This possibility is negligible in comparison to other risks which are secondary to thyroid cancer and therefore, the treatment of thyroid cancer should not be cancelled.




Preparation before Radioactive Iodine Treatment

Our Nuclear Medicine Specialist will assess your medical history regarding your thyroid gland, surgery/pathology reports, past imaging results and blood tests as well as doses administered in the course of past radioactive iodine treatments and s/he will also perform physical examination and request certain blood tests, when necessary, before radioactive iodine treatment is actually started.

Moreover, a beta-hCG test will be ordered for all women of child-bearing age.

You will need special preparation before the treatment since thyroid hormones (LT4, LT3) and medicines and food which contains iodine affect the success of radioactive iodine treatment.

You will be informed and guided about this issue during the appointment. Your strict compliance with these suggestions is very important for successful outcome of your treatment.


Cessation of Thyroid Hormone Replacement

If it is planned to stop thyroid hormone supplements before the radioactive iodine treatment, our Nuclear Medicine Specialist will plan the necessary replacement cessation schedule.

LT4 hormone supplements (i.e. Levotiron, Tefor, Euthrox, and Bitiron) should be stopped for at least 4 weeks and LT3 hormone supplements (i.e. Tiromel) should be stopped for at least 2 weeks.


Use of Recombinant TSH (rhTSH)

rhTSH (Thyrogen) is administered to hip muscle in 2 doses at 24-hour interval as an alternative to cessation of thyroid hormone replacement. Radioactive iodine is administered by mouth 24 hours after the last dose of rhTSH.


Low-Iodine Diet

Low iodine diet is an important component of preparation for tre eatment and should be started 2 weeks before the radioactive iodine treatment and maintained for 1 to 2 days after the treatment. This diet increases the success rate of radioactive iodine treatment.

Medicines Which Prevent Administration of Radioactive Iodine



Recommended Duration of Cessation

Thionamide medications (i.e. Propylthiouracil, methimazole, carbimazole)

3 days

Multivitamins that contain iodine

7-10 days

For natural/synthetic thyroid hormones, triiodothyronine (LT3 ,Tiromel)

10-14 days

For natural / synthetic thyroid hormones, thyroxin (LT4, Levotiron, Tefor, Euthrox, Bitiron)

3-4 weeks

Kelp, agar, carrageenan, Lugol solution

2-3 weeks, depending on the iodine content

Saturated solution of Potassium iodure

2-3 weeks

Topical iodine (i.e. surgical skin preparation)

2-3 weeks

Intravenous radiographic contrast agent, water-soluble

6-8 weeks

Intravenous radiographic contrast agent, fat-soluble

1-6 months


3-6 months or longer

Hair dye (containing iodine)

8 weeks


Food Products consumption of Which has to Be Stopped For 2 Weeks Due To High Concentration of Iodine




Iodized salt


Dairy products

Milk, yoghurt, cheese, ice cream

Egg yolk

Egg whites could be consumed.


Shellfish and fish

Turkey and liver


Algae and algae products

Carrageenan and alginate

Milk chocolate


Multivitamins that contain iodine


Products which contain red food dye (E127, erythrocyte ) (etc. hair dye, fizzy drink)



It could be consumed in small servings (1/4 of a plate) per meal.


Allowed Foods


Fresh fruit and vegetables

Salt-free peanuts/hazelnuts and hazelnut/peanut butter

Egg (white)

Fresh meat

Cereals/cereal products which do not contain iodine at high concentration (limited to 4 servings per day)

Pasta, which does not contain iodine at high concentrations





Black pepper

Fresh or dried weeds and spices

All vegetable oils [including soy oil]

Soda (which do not contain Red dye (E127))

Coke, Diet coke

Coffee (Not instant)

Tea (Not instant)


Fruit juices


What Can You Bring to Hospital?

You may bring a magazine/book, games, hand crafts/knitting equipment, cell phone, tablet or laptop for your spare time when you come for the treatment.

It is necessary to bring your daily clothes and sleepwear with you as you will wear them throughout your hospitalization.

We recommend to stop using contact lenses during the treatment period. Please bring your eyeglasses with you.

Radioactive iodine, which also implies radiation, will be present in your urine, sweat and saliva for a certain period of time due to the treatment. Therefore, your personal belongings may be contaminated by radioactive iodine. No problems will occur if these objects are used solely by you for the first several weeks after you return home. Contamination on your cell phone, tablet or laptop can be cleaned with a dampened cloth.

All clothes you used at the hospital should be washed separately from other clothes immediately after returning home.

Visitors will not be allowed throughout the hospitalization due to radiation safety measures.  However, you may contact our healthcare personnel 24/7 by phone.


How is Radioactive Iodine Therapy Performed?

Oral food and water intake should be stopped for 4-6 hours before radioactive iodine is administered and this restriction should be maintained for approximately 2 hours after the treatment. 

Radioactive iodine, which is planned for the treatment, is in liquid or capsule form and is administered by mouth in a special treatment room.

Your hospitalization varies depending on the planned dosage and results. This period generally lasts from 3 days to 1 week.

Total body radioactive iodine scintigraphy/SPECT/CT will be scanned in the Nuclear Medicine Clinic for 3-7 days after administration of radioactive iodine.

Patients with normal renal functions are recommended to drink 2.5-3 liters of liquid (except for milk) per day and void frequently for 1 week following the radioactive iodine treatment. Thus, radiation exposure of the urinary bladder and salivary glands can be minimized.

Defecation at least once a day is important for minimizing the radiation exposure of your bowels. You may use mild laxatives in case of constipation.

Flush twice after every use of the toilet in the hospital and at home for a period of several weeks. It is necessary for our male patients to urinate while sitting on the toilet during this period. It is necessary for you to wash your hands carefully following each visit to the restroom due to radioactive contamination.

You should take a shower every day during and for at least 1 week after your hospital stay; wash your towels, underwear and cloths separately afterwards.

It is necessary for you to wash your hands before meals, reading or holding something for a few weeks.

Prefer paper tissues instead of cloth and dispose the tissues by flushing it through the toilet rather than throwing it to a trash can.

Indication of inpatient treatment depends on the dose administered to the patient and is determined by relevant regulations.  Here, the aim is to protect family members of patients and the community from radiation.

Patients who receive radioactive iodine treatment at outpatient or inpatient settings are required to comply with certain precautions in order to be discharged. Patients who receive this treatment can only be discharged after the residual activity level in their body goes below the discharge limit which is determined in the regulation of the Turkish Atomic Energy Authority (TAEK). Our Nuclear Medicine Specialist will inform you in details, before you are discharged, regarding restrictions at your home, workplace and public places and about how long such restrictions will apply.

It is necessary for both male and female patients to use effective birth control methods with their partners and avoid pregnancy for at least 6 months following the radioactive iodine treatment.


Please contact us for further details.