What is radioiodine therapy?

Radioiodine as a radiopharmaceutical is one of the oldest and most successful radionuclide therapy treatments offered across the world. The thyroid’s natural absorption of iodine allows treatment of the thyroid that is non-invasive and highly targeted using radioactive iodine. Radioactive iodine has the same characteristics as the iodine found in food; however radioactive iodine emits radiation that is damaging to tissue.

The radioiodine is usually given as a capsule, no bigger than a typical paracetamol pill. It can also be administered as liquid mixed with water. Once in the bloodstream, the thyroid absorbs the radioiodine for the production of T3 and T4 hormones. The radiation given off by the radioiodine ablates (destroys) the tissue surrounding it, so when absorbed by the thyroid, it is able to deliver the radiation to a confined target.

The thyroid will not be able to absorb all of the radioiodine as it has a limited capacity. This is why prior to any treatment with radioiodine, either a low-iodine diet or an injection is necessary to increase the thyroid-stimulating hormone (TSH) for maximum absorption  of the radioiodine at  the  time of  administration.

What the thyroid does not absorb is filtered out of the blood and excreted predominantly through urine, but also through other bodily fluids such as sweat and saliva. In order to minimise the radiation exposure to other parts of the body, patients are requested to drink plenty of fluids as well as urinate and shower regularly.
Click here for more information on a low-iodine diet

There are two conditions where radioiodine may be used

1. Hyperthyroidism (Thyrotoxicosis)

Radioiodine is used for hyperthyroidism to ablate part of the thyroid. This ablation leads to a reduced volume of active thyroid, leading to a reduction in thyroid hormone production, including thyroxine (T4). The intention is for the hormone production to return to a normal level, however sometime the ablation may result in the thyroid becoming hypo. In this case, the hypothyroidism can be easily managed with the daily consumption of thyroxine tablets.

The fact that radioiodine is a non-invasive treatment of hyperthyroidism provides a clear benefit to the more invasive option of surgery.

Radioiodine treatment for hyperthyroidism is carried out on an outpatient basis in The London Clinic’s nuclear medicine department. The treatment involves clinical advice given by experienced nuclear medicine clinicians and radiation protection advice given by a medical physicist. The appointment will take around 30 minutes in total.

Radiation protection advice varies depending on the size of the dose prescribed but typical precautions include avoiding: 

  • Close (less than arm’s length) and prolonged (greater than 10 minutes) contact with ahildren under six and pregnant women for eight days
  • Close (less than arm’s length) and prolonged (greater than 10 minutes) contact with adults in regular contact (i.e. close friends, family members) for three days
  • Sharing a bed for five days

These precautions can typically be introduced into a daily routine without much hindrance. A medical physicist can discuss typical precautions prior to treatment.

2. Thyroid Cancer

Radioiodine is used to treat thyroid cancer. Typically, a thyroidectomy is carried out in order to remove most or all of the malignant thyroid disease. However adjacent to the thyroid are the parathyroid glands in which produce the parathyroid hormone. A surgeon will avoid damaging the parathyroid glands by compromising the thyroid tissue removal around these glands. Following on from surgery, the delivery of radioiodine will ablate (destroy) this remnant thyroid tissue with minimal damage to the parathyroid glands.

In some cases, malignant thyroid disease may have travelled away from the gland. A follow- up diagnostic scan uses an iodine tracer which, now with no thyroid to absorb the iodine, provides a very sensitive image of any remaining thyroid disease. In the case that further thyroid disease is observed, a higher therapy radioiodine dose may be given to ablate the disease.

Radioiodine treatment for thyroid cancer is carried out on an in-patient basis at The London Clinic’s Duchess of Devonshire Wing. Typical stay times are one to three days for ablations following surgery, and three to five days for the higher follow-up therapy dose. The treatment is carried out by an experienced nuclear medicine physician and a medical physicist is present to give radiation protection advice for both during the treatment and following discharge.

While an in-patient, the patient is limited to the room. Visitors are allowed but are requested to follow the advice of the medical physics team. Typically this involves a limited visiting time, limited contact with the patient, and personal protective equipment such as disposable gowns and gloves. Typical precautions following discharge include avoiding: 

  • Close (less than arm’s length) and prolonged (greater than 10 minutes) contact with children under six and pregnant women for eight days
  • Close (less than arm’s length) and prolonged (greater than 10 minutes) contact with adults in regular contact (i.e. close friends, family members) for three days
  • Sharing a bed for five days

These precautions can typically be introduced into a daily routine without much hindrance. A medical physicist can discuss typical precautions prior to treatment.

To make an enquiry about radioiodine therapy: