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I-131 treatment in case of bening thyroid diseases

The hyperthyroidism or the normally functioning but intumesce thyroid can be effectively treated with administration of 131 iodine isotope. The treatment has 60 years of history, its efficiency is verified by millions of successful therapies worldwide. As a result of therapeutic dose of the 131-I isotope into the gland the overproduction of thyroid hormone can be stopped, the normal metabolic state which is important for the body can be restored and the size of the thyroid gland can also be reduced. The treatment is painless and safe.


Course of the treatment

  • The treatment – depending on the isotope activity – has to be performed either in outpatient care or in a hospital.
  • 4 weeks before the therapy taking thyroid hormones (L-thyroxin) has to be discontinued.
  • Taking methimazole (Metothyrin) or propylthiouracil (Propycil) have to be avoided for a minimum of 3 days before the therapy.
  • Iodine have to be avoided. (The important iodine-containing preparations are the following: iodine contrast medium, amiodarone, expectorants, didinfetants for example betadine, trace elements preparations, medicinal waters, dietary supplements for example sea algae).
  • In 2 weeks prior to the therapy a low iodine diet is recommended (food which contain significant amount of iodine: iodized salt, sea salt, milk and dairy products, iodized bread, sea fish, celery, iodine-containing multivitamins, food that contain red food dye, horse-radish, marinated and smoked food, soya, hamburger).
  • About the medications taken by the patient the therapist decides whether any of them has to be discontinued temporarily.
  • The fluid or capsule which contains the isotope has to be swallowed on an empty stomach and after that patients should not eat anything for an hour.
  • After taking the isotope-containing capsule or fluid an excessive fluid intake is recommended, 2-3 litres daily at least for 3 days.
  • In case of ambulatory treatment patients have to wait isolated for at least 2 hours at the department of nuclear medicine where the therapy is performed.
  • If necessary 2 weeks after the radioiodine therapy inhibitors (Metothyrin, Propycil) can be taken again on medical advice and have to be continued until the radioiodine takes its effect.


The therapy is contraindicated

During pregnancy and breast-feeding. After discontinuation of breast-feeding minimum 6 weeks have to pass until performing a radioiodine therapy is recommended.


Side effects

Right after the therapy especially in case of high doses nausea, swallowing of the thyroid gland, possible pain and temporary worsening of the hyperthyroidism symptoms may occur rarely.


Late side effects:

  • The most important is the hypothyroidism. The incidence of this depends on the type of the disease, but in the first place it can be observed in case of Basedow-Grawes disease. Several times it occurs years after the therapy, the probability of appearance can be up to 60% ten years after the radioiodine therapy. With taking thyroid hormone-containing tablets the lack of this hormone can be substituted perfectly.
  • Deterioration of eye symptoms can be observed in approximately 5% of the cases.
  • Based on the experience gained from cases of large number of examined patients it can be securely stated that radioiodine therapy of bening thyroid diseases does not increase the risk of thyroid cancer.


Regulation of radiation protection during hospitalization.

  • After taking the capsule (fluid) the patient is only allowed to stay in the isolated isotope therapeutic section until the therapist permits leaving the closed area.
  • It is not permitted to have visitors in the isolated area.
  • It is only permitted to use the assigned toilet.
  • Rules on personal hygiene and radiation protection have to be kept.


Regulation of radiation protection after discharging the patient

Because of the therapeutically administered radioiodine the patient has to be ragarded as a radiation source. That is why the longer the distance between the patient and the environment is, the lower the radiation load is for other people. If someone stands 2 m away from the patient he/she is exposed to one fourth, if standing 3 m away he/she is exposed to one ninth of the radiation of the amount in case someone is standing only 1 m away. The shorter time someone stays in the surroundings of the patient (in this case the source of radiation) the lower the radiation load time-proportionally is.

Regulation of radiation protectionActivity of the administered I-131:
<250 MBq250-550 MBq
For how many days?
Not permitted to take public transportation-4
Not permitted to be within 1 m to an other person for longer time24
Not permitted to be in the same room with children and pregnant women714
Providing a distinct toilet for family members under the age of 35 living in the same household35
- Men should also use the toilet seated
- Thorough hand-wash after using toilet
- Flushing the toilet 2-3 times after using
Excessive fluid comsumption11
Using distinct bed-linen, washing the bed-linen and the underwear separately77
Using of distinct cutlery77
Can go back to work as soon as:After 2 daysAfter 4 days


Breast-feeding, pregnancy

  • If a breast-feeding women is treated with I-131 the lactation has to be terminated and after going home it cannot be continued. Women treated with radioiodine because of a bening thyroid disease have to avoid becoming pregnant for 6 months. If pregnancy yet occur, the family physician has to be informed about it immediately.
  • Men treated with radioiodine should not procreate a child in four months after the therapy.
  • In case of offsprings of mothers and fathers treated with radioiodine, increased incidence of developmental abnormalities have NOT been observed.


Hospital treatment due to other diseases

If during the restriction period after the isotope therapy the patient is unexpectedly hospitalized, the nuclear medicine specialist (who treated the patient with radioiodine) and the family physician has to be informed immediately.



In 3 months after the treatment for crossing borders and entering protected buildings you may need to take the Certificate or Discharge papers and the English certificate with you. These documents provide an explanation if the highly sensible radiation gate gives a warning signal.


Experiential patient information

  • Isotope therapy is performed on an empty stomach (drinking fluid is permitted).
  • After taking the capsule patients are not allowed to eat for an hour.
  • On the day of the treatment patients should drink an excessive amount of fluid.
  • In 2 days after the therapy the patients should use a distinct toilet and should flush it 2-3 times after using.
  • Men should also use the toilet seated.
  • During the first 2 days preferably do not have visitors, younger children and pregnant women do not visit him/her.
  • If possible, patients should not leave their rooms.
  • Use distinct cutlery for eating.
  • If the floor or the bed is contaminated with urine, stool or vomit inform the medical team (do not start to clean it and do not step into it).
  • The necessary actions are taken by the professional crew.
  • If the patients experience any ot the side effects described in the patient information leaflet, they have to inform the nurse who will call for the physician.
  • About leaving the therapeutic unit the isotope specialist decides after performing dosimetry.
  • The patient has to strictly keep the above mentioned rules in order to protect himself/herself, family and medical staff.