Transcript of webinar Q&A session on Radioiodine Therapy (RAI) to treat hyperthyroidism 

We welcomed two consultant endocrinologists and a nuclear medicine physicist to our April ‘Meet the Thyroid Experts’ webinar. Our 200 strong audience heard from Dr Glenn Flux, Head of Radioisotope Physics, Royal Marsden Hospital, Surrey. Glenn gave a fascinating explanation of radioiodine therapy, including a potted history of its pioneers.  

Dr Steve Heyer, consultant endocrinologist, Royal Marsden Hospital then explained more about RAI, when it might be suitable and the risks versus benefits of available treatments for hyperthyroidism. The meeting was expertly chaired by Dr Salman Razvi, consultant endocrinologist, Queen Elizabeth Hospital, Gateshead.  

This is a transcript from the webinar Q&A session. 

Key  

SH - Dr Steve Heyer 

SR – Dr Salman Razvi 

GF – Dr Glenn Flux 

I have a strong family history of breast cancer. Would you still consider RAI suitable? 

From a physics point of view, yes. There is no reason why there is a bigger predisposition to radioactive irradiation (radiation exposure). (GF) 

How long would someone having RAI for Graves’ disease typically need to stay away from children? 

There are a lot of different ideas on this, so I am not going to give a definitive answer. Because of these variations in views there is a working group in the UK to see if we can consolidate and get some agreement on what those discharge criteria would be. 

It is difficult to say without knowing the radiation dose. In this country, it could be 400 megabequerels* or it could be 800 megabequerels.  Everyone should get this information from their clinician or from their physicist at the hospital. And I would say very strongly that if you are not happy or not clear then press again for an answer. You should be very clear on what the criteria are. (GF) 

In our hospital, we typically advise around 14 days to stay away from children but I take your point around that. (SR) 

* megabequerels = a unit of measurement of radioactivity 

How long is it safe to delay RAI or thyroid surgery a year after starting Antithyroid Drugs (ATD)? 

I am not sure there is a safety element; it is more of a clinical concern to normalise the levels as much as we can. (SR) 

I agree. As long as your levels are good, you can wait as long as you like. (SH) 

After RAI is it likely the immune system will attack another part of the body? 

There is no evidence of this. (SH) 

Has anyone started to consider using Radio Frequency Ablation (RFA) instead of RAI? 

Yes, it can be used to treat thyroid nodules and RFA is becoming a popular, pretty non-invasive way of treating lumps in various organs. However, for Graves’ disease where the whole thyroid is affected, RFA would not be a feasible option. (SH & SR) 

My thyroid levels have been stable for years on levothyroxine after receiving RAI. However, they’ve now gone haywire. Why is this if I don’t have a thyroid? 

This could be to do with a number of things including how and when you take your levothyroxine, other medication interfering and weight changes. (SR) 

Yes, at the Royal Marsden we have a thyroid absorption test where we measure patients’ TSH and thyroid hormone levels. We then give them levothyroxine under supervision to define what is going on. In a small number of cases, we see the levothyroxine disappearing very quickly from the patient’s system, usually due to a problem with the binding protein. More often than not, it is interfering substances but when given under the right conditions, most patients absorb the levothyroxine perfectly well. So, you have to pay a lot of attention to how patients are taking their levothyroxine and also to which brand they are taking. (SH) 

How long does it take for the radioactivity to disappear after RAI? Will it go immediately or will I have to stay on ATD for a while? 

It does not go immediately. In some patients, their thyroid levels have come down when we review them at six weeks. In other patients, it can take up to six months. We would not even consider giving another dose of RAI before six months. Generally, it is a matter of weeks to months. (SH) 

How often will I have check-ups after RAI? I’m nervous I will go hypothyroid and it won’t be picked up. 

Any RAI centre should offer you a treatment plan. This will offer you follow-up tests at set intervals or sooner if there are symptoms or new symptoms. This will typically be at six weeks, three months, six months and one year after RAI. (SR) 

We do not usually need to see patients as we do this via virtual clinics. You will be given a series of blood test forms and we monitor them. We may need to see you in some cases though. (SH) 

Is RAI ever considered for hyperthyroid patients with Thyroid Eye Disease (TED)?  If so, are there any precautions patients can take before undergoing treatment? 

Yes, we do give it to patients with mild cases but only with steroid cover. We would have an ophthalmologist to assess whether the TED is stable, ie. burnt out prior to doing RAI. We would not give RAI in patients with active TED. (SH) 

What risk do you quote of developing TED to patients having RAI? 

I do not quote risk in terms of numbers as it is very individualised. I refer patients to BTF patient literature, which explains more about RAI. If I could explain the difference between relative and absolute risk though. If I buy two lottery tickets, I increase my chance of winning but my absolute chance of winning remains infinitesimally small. So, your absolute risk of getting these problems is very low even though your risk is increased. (SH) 

Will I be screened for TED before undergoing RAI? 

The process starts by being referred to a specialist endocrine clinic. Your endocrinologist will know how to score your eyes. If we are worried about a patient’s eyes, or they have a high clinical activity score, then we refer the patient on to an eye clinic to be seen by an ophthalmologist. Your pressures will be measured, and you will have a thorough assessment. So, the process starts with referral to an endocrinologist and we go from there. (SH) 

Why are endocrinologists anti-ATDs? 

We actually give out ATDs all the time in our clinic! We want to do the best for our patients but their views must be taken into account. All treatments can cause problems and there are none that are 100% safe. We do not have a preference. We try to balance out the pros and the cons for the individual in front of us. (SH) 

How long do I need to be off work after RAI? Does it depend on what job you do? In my job, I’m required to work in close contact with people. 

It is difficult to generalise. If you have lots of close contact in your job or work with children then you would probably need to stay off for longer. You need to have a discussion with your treatment centre and make sure you are happy with the answer. (GF) 

How long does it take to recover from RAI?  

Everyone is different and it depends on a number of factors, such as the underlying cause of the hyperthyroidism, the dose etc. So, there is no one size fits all answer. (SR) 

Would RAI be suitable for a hyperthyroid patient with both blocking and stimulatory thyroid antibodies, that alternates between hyperthyroidism and hypothyroidism with Graves’ disease? 

This is an interesting question and one that probably requires a bit more research to give a definitive answer. It is the case that some hyperthyroid patients with blocking antibodies go through a hyper phase then become spontaneously hypothyroid. So, it would be wrong to give RAI to these patients as they will eventually become hypothyroid anyway. However, it is not an absolute and we do use RAI in some patients with blocking antibodies. Assessment is key though most centres that measure TSH receptor antibodies as a stimulatory antibody do not have a bioassay to measure whether it is stimulatory or blocking. It is a complicated business. For example, it is possible that you can have a hypothyroid patient with TSH receptor antibodies that are blocking.  (SH) 

Does RAI reduce fertility in men and women? Can it cause birth defects? 

We did a fertility study some years ago, which showed that RAI did not affect fertility. We did notice a hormonal change but no effect on fertility. 

In terms of birth defects, the key one to worry about is the thyroid of the foetus. This develops early on during the first trimester. If a woman is exposed to RAI at this time, the iodine will go into the foetus’ thyroid and destroy it so that is the main one. I am not aware of any other ones linked with RAI. 

There is a birth defect which can be linked to carbimazole. This is called cutis aplasia. This is a scalp defect. It is exceptionally rare but I have seen one case of it. (SH) 

How does RAI know how to target the thyroid and not other organs of the body? 

Iodine is the heaviest element of the body. It has a very specialised function. It is taken up by special receptors on the cellular surface and incorporated into thyroid hormones. It is also taken by some other tissues including breast and the salivary glands, but not to the same extent. (GF) 

Does RAI alter the genetic makeup of your body? 

No (GF) 

I had a partial thyroidectomy to treat Graves’ disease in 1997. I have since become hyperthyroid again. A scan has shown my thyroid has regrown to 6/8 of its original size. Is RAI suitable for thyroid regrowth? 

I would suspect there was a sizeable remnant after surgery for it to have regrown to this extent. Yes, RAI would be ideal in this situation and probably at an ablative dose. (SH) 

My friend had a thyroidectomy following thyroid storm 40 years ago. They left a sliver of her thyroid and she’s never gone underactive as a result. Would surgeons consider leaving a sliver in patients to prevent them becoming underactive? 

This is really a question for surgeons, and we do not have one here today. This is very unusual and I would say your friend was incredibly lucky not to develop hypothyroidism or, depending on how much was left, to become hyperthyroid again. You do not really want to be performing repeated operations on patients so that is the main reason we do not leave thyroid remnants in patients, especially in those with Graves’ disease. (SR) 

How likely is it for patients not to become hypothyroid after RAI 

Occasionally we see patients who remain euthyroid, that means their thyroid levels are good, for many years. In some cases, they only become hypothyroid after 10 years or more. This is more likely where we administer a low RAI dose. I would argue this is an advantage for a patient to stay euthyroid for as long as possible. So, yes there can be a delayed effect on thyroid function after RAI. (SH) 

Can people be treated lifelong with ATD rather than be offered RAI or surgery to destroy the thyroid and consequently be on lifeline treatment for hypothyroidism? 

Yes, they could and I do have some patients on lifelong ATD treatment. From a personal view, would I prefer to be on natural, normal thyroxine albeit in a synthetic form but in all other ways identical to that which the body produces? Or would I rather be on a drug that inhibits thyroid production? I would go for the natural, normal thyroxine but that is my personal opinion. (SH) 

I have been on Propylthiouracil (PTU) for several years and feel like my doctor is pressurising me to go down the RAI route. Do I have an option?  

No-one can give you treatment against your will. Have a conversation with your endocrinologist and ask them what their concerns are about staying on PTU long-term and why they are recommending RAI to you. (SR) 

Yes, I would say as long as people can make an informed choice based on all the facts, then fair enough. (SH) 

And what about staying on carbimazole long term?  

Again, it is about making those informed choices based on all the facts available. Certainly, being on a low dose of carbimazole (under 30 mg) is safer than being on a higher dose. (SH) 

Is there a protocol for mitigating any potential long-term adverse outcomes of RAI? 

Yes, we do mitigate risks by ensuring the following prior to RAI: 

• The blood levels are good 
• Assessing the eyes 
• Giving steroids if necessary 

We also closely monitor the patient. All these are good practice and are mitigations I would argue. (SH) 

If Graves’ disease antibodies are still present after RAI, can they attack the eyes or another organ of the body? 

They cannot attack another organ but it is possible they can attack the eyes. That is why it is possible to develop TED after RAI. At the moment, we do not use immunotherapies to try to reduce antibodies. Instead, we treat the organ being attacked, i.e. the thyroid. In the future, we may take a totally different approach which could involve trying to remove or neutralise the antibodies responsible. However, these treatments are still at the research stage. (SH) 

What is the difference between RAI and a radioisotope uptake scan? 

The radioiodine is the radioactive drug you take. I-131 is an isotope of iodine. The isotope uptake scan is an image that shows where the radioactivity goes to. (GF) 

Does RAI affect the liver in the same way that other medications can if taken long term? 

No (SH) 

When taking carbimazole and levothyroxine as part of a ‘Block and Replace’ treatment regimen, does there need to be an hour’s gap between taking the two or can I take them at the same time? 

They can be taken at the same time when on ‘Block and Replace.’ (SH) 

Is the dose and way of administering RAI different for teenagers compared with adults? 

No, I am not aware of any real changes in dose for teenagers compared with adults (SR) 

If Graves’ disease is a cause of hyperthyroidism, why don’t you treat the cause, rather than the symptoms? 

That is a very good question, and we are working on it. There is some research going on, particularly in Newcastle, looking into ways of treating the cause. Although we know the antibody sets off the process we do not really understand what causes the antibody in the first place. We know certain people have a tendency to make the auto antibodies but we do not really know why you develop Graves’ disease today but not six months ago. I am sure we will be treating Graves’ disease completely differently in the future. (SH) 

I’ve been on PTU for five years and have now been offered RAI, I have lots of allergies so am worried I might not be able to tolerate levothyroxine. 

Levothyroxine is one of the most well-tolerated drugs and problems with it are incredibly rare. (SR) 

Where there are allergies to it, it is usually to the excipients (fillers) that are used in the tablets, not to the levothyroxine itself. If a patient were unable to tolerate a certain formulation, we would try them on a different brand. I have not yet come across any patient who we have been unable to find a suitable formulation of levothyroxine for. (SR) 

How does a standard non-personalised dose of RAI work if the patient has restricted growth? 

The size of your thyroid is not necessarily linked to your overall size. We see large thyroids in short people and vice versa. It is controlled by different mechanisms to your growth. (SH) 

I have a small goitre with Graves’ disease. Will it disappear if I have RAI? 

Probably. When we say goitre what we mean is a vascular thyroid and that is reflected in the activity of the Graves’. So as the thyroid hormone levels reduce, the size of the goitre will probably shrink too. (SH) 

How likely is it I will need a total thyroidectomy if my RAI fails? 

This would be very, very unusual because if the RAI ‘fails’ we can give another dose. It is unusual to find a thyroid that will not respond to a sufficient dose of radioiodine. I guess there may be the odd case where surgery may be offered. For example, if the radioiodine is not being taken up for some reason or the patient is no longer suitable for radioiodine. (SH) 

I had RAI 30 years ago. The antibodies weren’t checked then. As I do not have Thyroid stimulating hormone receptor antibodies  (TRAb) now I how do I know even had Graves’ disease? How long do TRAb stay raised as I would like to know the original reason why I had RAI? 

The reason we suggest 12-18 months on ATD for patients with Graves’ disease is because we think at the end of this period the antibodies will have largely gone and some patients are in remission. 

Of course, it does not always go that way. Some centres will re-measure antibodies after 12 months. We did start doing that at my hospital but we found it was not very helpful. For example, some patients with antibodies remained in remission whereas others with no detectable antibodies relapsed. The answer is everyone is different.  

The relapse may be about another form of immunity which we call cellar immunity or T-cell immunity. So, immunology is another big complicated area that could be explored at a separate webinar. (SH) 

I gained weight during my hyperthyroidism phase. I am concerned that RAI will make the weight gain worse, especially as I have a family history of heart disease. 

Weight is a funny thing. Two things happen with hyperthyroidism: Your metabolic rate increases and your appetite increases too. Normally, hyperthyroid patients will lose weight. In some cases, particularly in older people, appetite stimulation is greater than the increase in metabolic rate so they will gain weight. 

It seems to be related to brown and white fat. Brown fat is more sensitive to thyroxine and some people tend to have more brown fat. These people tend to be able to eat what they want and never put on weight. White fat is metabolically less active and people with lots of white fat tend to struggle more with weight gain. 

In terms of whether you will gain weight after RAI treatment. All RAI is doing is rendering you euthyroid. 

I have multiple health problems. If I undergo RAI for my Graves’ disease could this make my other conditions worse? 

Not as far as I am aware. As Glenn so eloquently explained, radioiodine is a ‘magic bullet’ which targets the thyroid and doesn’t go into other cells. (SH) 

Will RAI shrink my goitre? 

RAI will shrink a smooth thyroid but it will not do much for a nodular thyroid. (SH) 

Should everyone be put on a low dose of prednisolone (steroid) before RAI to prevent the possibility of developing TED after RAI? 

It is not recommended to give steroids. This is because the incidence does not justify the risk of the steroid use. However, if TED is picked up when the patient is assessed prior to RAI then we would probably commence them with a course of steroids. (SH) 

What symptoms would you expect nine months after having RAI? 

There should not be any symptoms in relation to the RAI procedure itself after this time. However, some patients may experience symptoms related to hypothyroidism. Others may get hyperthyroidism symptoms if there is a recurrence of this. (SR) 

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