I-131 therapy - Morkel Nuclear Medicine
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I-131 therapy

What is hyperthyroidism?

Your thyroid gland is situated in your neck. It produces a hormone called thyroxine. This hormone is important for your metabolism and has an effect on multiple organ systems. If your gland becomes overactive it means that it is producing too much of this hormone and this increases your metabolic rate. This is why symptoms may include palpitations, anxiety, flushes, weight loss and insomnia (difficulty sleeping) and why treatment of your overactive thyroid is so important.

What is radioactive Iodine?

The thyroid gland uses Iodine that it takes out of your daily diet to produce thyroid hormones. Radioactive Iodine is Iodine that is combined with a radioactive source. It easily reaches the thyroid gland where it gives off radiation to reduce the production of the thyroid hormones and it reduces the activity of the thyroid gland.

What does radioactive Iodine look like?

Radioactive iodine comes in a capsule form. It is colourless and tasteless. It is taken with water and you can continue with normal daily activities (eg driving) thereafter. The amount of Iodine in the capsule is so small that it can even be given safely to people with an allergy to Iodine. The dose is calculated and ordered specifically for you

Is radioactive iodine therapy dangerous??

NO! Radioactive Iodine has been used since the 1950’s to treat an overactive thyroid. During the years it has proven to be a safe and an effective way of treating an overactive thyroid. Multiple studies have been conducted and it has been proven that the treatment itself does not cause an increased risk for developing cancer later in your life.

Are there any side-effects?

Side-effects are highly unlikely. Some people may experience some pain in their throat or an increase in the symptoms they experienced before the therapy; however this usually improves within 10 days.


A common result is that the thyroid becomes underactive after the therapy. This is however easily treated with a tablet that you will have to take daily.

Before and after the treatment.

Certain thyroid medications will need to be stopped before the treatment. Please discuss this with your referring doctor or nuclear medicine specialist.


After the treatment your body will contain some radioactivity. It gets excreted in your urine and will reduce every day; however we do advise that you limit contact with small children and pregnant women for the first few days after the therapy.

Can I have this treatment if I am pregnant or breast feeding?

No. We will not administer the therapy if you are pregnant or breastfeeding. If you are breastfeeding you must stop for at least 2-4 weeks before the therapy and you must NOT resume breastfeeding after therapy. Breastfeeding may be resumed with your next child.


Please inform us if you think you may be pregnant.

Will I be able to fall pregnant again after this therapy?

YES! But you should not fall pregnant within 6 months after the therapy and we therefore advise you go on contraception for this period. Men should also not father children for at least 3 months after the therapy.

Will I need to see a doctor after the treatment?

Yes, you will need to see your referring doctor 6-8 weeks after the therapy. A blood test will then be done to see how the thyroid responded to the treatment.

How many treatments will I need?

Most people respond well after just 1 treatment; however in about 10% of people more than 1 dose is needed.