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Thyrotoxicosis Information

Background/Introduction

Thyrotoxicosis (or hyperthyroidism) is an over functioning thyroid. This can be treated with radioiodine (radioactive 131Iodine (131I)) which, after entering the bloodstream through ingestion, targets only the thyroid cells in the body. This form of radiation treatment can be referred to as “radioiodine therapy”.

At QAH, thyrotoxicosis will be treated with a course of antithyroid drug (ATD), such as Carbimazole or Propylthiouracil (PTU). For patients that have suffered a relapse and have already undergone ATD therapy, radioiodine therapy is provided. The aim of the radioiodine therapy is to return the thyroid to a euthyroid (normal) state, although the thyroid activity may go under (hypothyroid) or remain above (hyperthyroid) the euthyroid state. If you remain hyperthyroid, another radioiodine therapy may be subscribed, if you become hypothyroid you may have to take Thyroxine (T4) for the rest of your life.

Radioiodine Therapy for Thyrotoxicosis

If you are prescribed radioiodine therapy for the treatment of thyrotoxicosis, you will be asked to attend one of our thyrotoxicosis clinics in the Nuclear Medicine Department (C-level) at QAH. The treatment is given in the form of an iodine capsule which is swallowed. The capsule is smooth and is approximately the size of a Paracetamol. However, if you are unable to swallow capsules, it may be possible to drink the radioiodine in the form of a liquid instead.

When you swallow the capsule, its outer coating dissolves and the radioactive iodine is absorbed into your bloodstream. As the blood
circulates around your body, any thyroid cells will readily absorb the radioactive iodine in the same way as non-radioactive iodine is
absorbed from the diet. The uptake of iodine in the body is strictly limited to thyroid cells, which means the radiation is targeted to only where it is needed. The radiation will cause some thyroid cells to stop reproducing while retaining their function, thus causing the overall activity of the thyroid to reduce.

For several weeks after you swallow the capsule, you will be radioactive. Any radioiodine that is not absorbed by your thyroid will pass out of your body through all bodily fluids (predominantly urine). The regulations governing radiation state that we need to limit the radiation dose received by people who do not need it. Patients are therefore required to follow restrictions on the contact and interactions that are had with others. You will be given a written sheet with details of all the restrictions and the Nuclear Medicine staff will advise you in more detail during the clinic.

Patient Preparation & Restrictions

To undergo this treatment, you will be required to go on a low iodine diet for 1 week prior to treatment. Also, for 2 hours before and after administration you will not be allowed to consume any food. This is to allow the radioiodine administered to work as effectively as possible.

As you will be radioactive, there will be some restrictions that you have to follow after the treatment. These are dependant on the activity that you are prescribed and will be given to you before the treatment date so that you can prepare in advance.

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Last updated - 16 August 2019
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