Iodine-131 Therapy

Authors: Mrs Claire Du Jardin*
                            Dr Dee Nandurkar *

What are the prerequisites for having Iodine-131 therapy done?

Endocrine specialists generally refer patients for these treatments.

All women who are not yet menopausal must have a blood test on the day of the treatment to ascertain pregnancy status. This is at the nuclear medicine physician’s discretion.

For patients having an ablative dose as a result of carcinoma, TSH levels must be >30 and patients must be off thyroid medication.

For thyrotoxic patients Neomercazole etc. must be ceased. Check with the administering department for their policy on the cessation period for these drugs.

What are the absolute contraindications for Iodine-131 therapy?

Pregnant patients must not be treated with Iodine-131.

Breast feeding patients should not breast feed following a treatment. Nuclear medicine staff in consultation with the patient will decide how long to withhold breast milk.

The time depends on many factors and is impossible to predict. Different facilities and physicians have different views and will consider the patient’s condition, dose, etc., when making this decision.

What are the relative contraindications for Iodine-131 therapy?

Care should be taken with patients who have large remnants post thyroidectomy. A dose that is too high can result in complications.

What are the adverse effects of Iodine-131 therapy?

With all Iodine-131 treatments, the dose given is an estimation. Each patient responds differently and it is up to the referrers in conjunction with the nuclear medicine physicians to find the most appropriate dose for each patient. For patients with thyrotoxicosis there is a risk that the dose will be too high and the patient experiences hypothyroidism. Alternatively, the dose may not be enough in which case a subsequent treatment may be required.

Generally, patients undergoing treatment for an overactive thyroid gland will not experience any side effects from the treatment as their dose is quite low.

Those undergoing treatment following removal of the thyroid as a result of carcinoma may experience some side effects including dry mouth and salivary gland pain. This can be alleviated by sucking on lemon lollies to stimulate saliva production. Nausea is less common and can be controlled by administering anti nausea medication.

Are there alternative imaging tests, interventions or surgical procedures to Iodine-131 therapy?

Iodine-131 is generally the treatment of choice for post thyroidectomy carcinoma patients and patients with difficult to manage thyrotoxicosis.

Further information about Iodine-131 therapy:

Recombinant TSH or Thyrogen administration in the days leading up to Iodine-131 therapy allows post thyroidectomy patients to have ablation whilst on their hormone therapy. This alleviates the stress of hormone withdrawal leading up to the treatment. How long patients will need to follow these precautions will depend on the dose, living conditions and the department where the dose is administered. A good guide is 2 days from when the patient goes home (regardless of whether they had the dose as an inpatient or outpatient).

General precautions for outpatients <15mCi dose:

  • Do not kiss people, especially children or pregnant women. This is to prevent transfer of iodine via saliva.
  • Do not allow children to sleep with them for the next 2 nights following therapy. Can give children brief cuddles but try to avoid long periods of close contact.
  • Do not share eating utensils, cups, drinks, ice-creams etc.
  • Always flush the toilet twice to clear away iodine that has been excreted in urine. Wash hands well after using the toilet. Other people must wear gloves and wash thoroughly if handling urine or urine contaminated items.
  • Casual contact with adults is acceptable. Try to keep contact to a minimum (short times and maximum separation) and avoid prolonged close contact eg. cinema, travel.
  • Contraception is advised for at least 3 months. This can be discussed with your patient.
  • Drink plenty of fluids to assist in washing excess radio-iodine from the body.

Useful websites about Iodine-131 therapy:


*The author has no conflict of interest with this topic.

Page last modified on 26/7/2017.

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