Thyrotoxicosis and Treatment with Radioiodine
Why do I need radio-iodine treatment?
You have a condition called thyrotoxicosis. This means your thyroid gland is overactive, producing too much thyroid hormone (thyroxine). Symptoms of an overactive thyroid include tremor, excessive sweating, palpitations and weight loss. Some patients have no symptoms, but if it is not properly treated, your health may be affected in the future. We also use radio-iodine treatment to shrink goitre, (enlarged thyroid gland). In this case, the thyroid gland may not be overactive or may be just on the borderline.
What is radio-iodine treatment?
Radioiodine is a colourless liquid containing a radioactive form of iodine. The thyroid gland uses iodine from the diet to make thyroid hormone. Radioactive iodine will concentrate in the gland in the same way as normal iodine, so only a small amount of radioactive iodine is required. The dose of radiation to the thyroid gland stops it producing so much thyroid hormone. This type of treatment has been used all over the world for over fifty years and is a well accepted way of managing an overactive or enlarged thyroid gland.
Before radioiodine therapy. What may I eat?
A diet which is rich in iodine can reduce the effectiveness of the treatment, so we offer the following suggestions:
- If you take multivitamins, or minerals containing iodine, cod liver oil, cough medicines, seaweed preparations or use iodised sea salt, these should be stopped one week before the radio-iodine treatment. (Many of these contain iodine.)
- One week before treatment, cut down on fish and seafood, dairy produce such as eggs, cheese, milk and milk products.
How is the treatment given?
Patients attend for an outpatient clinic appointment in the Department
of Nuclear Medicine at Poole Hospital.
The treatment consists either of a small drink or a small capsule. You
may eat and drink normally before the treatment, but we ask you not to
eat or drink anything for two hours afterwards. This will help you to absorb
the radio-iodine more quickly.
Will I feel ill afterwards?
No. Most patients have no side effects from the treatment. Occasionally, there is a mild ache in the neck area for a few days.
How many treatments will I need?
Most people need only one treatment. Sometimes, the amount given is insufficient, and a second or even third treatment is necessary. The blood tests after your treatment will show whether further treatment is necessary. If further doses of radio-iodine are required, we usually wait for 3-6 months before repeating it.
How quickly will the radio-iodine work?
The effects are gradual over a few weeks.
How long will the radio-iodine stay in my body?
Only a short time. Most will be concentrated by the thyroid over 2-3 days. We ask that you drink plenty of fluids during this time. The rest will be passed from your body in urine with a tiny amount leaving in saliva and perspiration.
What if I am taking anti-thyroid medication?
Carbimazole or propylthiouracil must be stopped 7 days before treatment, to allow the radio-iodine a better chance of working. We do not usually restart the carbimazole or propylthiouracil after the iodine treatment, but wait to see the effect. It is more effective if these drugs are avoided immediately afterwards. A blood test for thyroid hormone should be taken four weeks after the radio-iodine dose.
If you feel that you have severe symptoms of thyrotoxicosis after the iodine, have the blood test taken sooner and contact your GP who will have the results in 3-4 days. If the blood test confirms thyrotoxicosis, your anti-thyroid treatment can be restarted. It is most unusual for this to be required within 4 weeks of iodine treatment.
What happens if I require other sorts of medical treatment?
You should continue to take any other medicines prescribed by your doctor. You will be given an Instruction Card when you have your treatment. Please show this card to any doctor who is treating you.
Can radio-iodine treatment for an overactive or enlarged thyroid cause cancer?
Radio-iodine has been used successfully for the treatment of thyrotoxicosis for more than 60 years. Patients treated in this way have been studied very carefully over many years. There appears to be no overall increased risk of developing cancer as a result of this treatment.
Are there any risks in having children afterwards?
No, not in the long term. But, you should avoid pregnancy or fathering a child for 4 months following radio-iodine treatment. You should not breast feed a baby at this time. There is no risk of abnormality to children and no risk of infertility if this advice is followed.
Are there any long term side effects?
Radio-iodine is a very safe treatment. However, your thyroid gland may become underactive, that is stop working, after the treatment. This could happen within a few months, or many years after treatment. Regular checks of thyroid hormone levels are required to detect an underactive thyroid at an early stage. We recommend a blood test for thyroid hormone levels four weeks after radio-iodine treatment, then every 2-3 months for the first year. Thereafter, an annual check is recommended.
What happens if my thyroid does become underactive?
Underactivity of the thyroid is easily treated with natural thyroid hormone, thyroxine. This is very safe and at the correct dose has no side effects. Thyroxine tablets are taken once a day and your GP will monitor the dose with annual blood tests. You will be entitled to exemption from prescription charges, using a form from your GP surgery.
Are there any special precautions I have to take?
The main disadvantage of radio-iodine treatment is the inconvenience of the radioactivity. The radiation dose will be good for you as it is a very effective treatment for your thyroid problem. At the same time, people close to you during the few days following your treatment will be exposed to a small amount of radiation from the radioactivity in your thyroid. You can take steps to reduce this by following the precautions given on the Instruction Card.
Will I have to stay off work after the treatment?
Most patients can return to work immediately. However if your job involves:
- handling food
- working in close proximity to the same individual for most of the day
- working with children
there may be some restrictions. Please discuss this with the physicist-in-charge
in the Nuclear Medicine Department. You can do this before your treatment
to enable you to make plans accordingly.
This is not because you will feel unfit for work, but to avoid radiation
to others. If you handle photographic film or are a radiation worker
you should also advise us, as special instructions may be necessary.
Is there any danger to my family?
No. But to avoid any unnecessary radiation to your family, please follow the written instructions on your Instruction card for Patients who have had Radionuclide Therapy.
This card will be given to you when you have the treatment. You MUST keep the card with you until the date specified.
What are these precautions?
The precautions given to you will depend upon your personal circumstances, and the dose given. They will be discussed with you prior to treatment. They will include the following:
- flush the toilet twice after use,
- wash hands carefully before preparing food for others,
- avoid non-essential close contact (less than 1 metre) with young children and pregnant women (this may be for up to 24 days)
- if necessary, sleep apart from your partner - separate beds if feasible,
Will I need to see a doctor after the radio-iodine treatment?
Yes. You will need to have a blood test four weeks after the treatment and attend clinic at 6-8 weeks. This will allow us to check how your thyroid gland has responded.
If you have any further questions after reading this information
please contact:
The Nuclear Medicine Department (01202) 442499
Further information
British Thyroid Foundation
PO Box 97, Clifford
Wetherby
West Yorkshire LS23 6XD
References
This information has been produced by:
Dr W Gatling, Consultant Physician
Dr M Armitage, Consultant Physician
Mr L Jansson, Head of Nuclear Medicine
Date produced: February 2007
Review date: February 2008
