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  • Clare Reed CBT Therapist

The Link Between an Under-Active Thyroid and Radiation

The Link Between Hypothyroidism and Radiation
The Link Between Hypothyroidism and Radiation

Life as a Stage 4 Cancer patient is full of scans, endless and unrelenting. So far, I have been fortunate to have ‘all clear’ scans for 18 months now since my metastatic brain tumour was diagnosed. In that 18 months I have been subjected to 3 full body PET CT scans with radioactive iodine pumped through my veins. And 1 hip X-Ray and 1 body CT scan, in this last week, without radioactive iodine. This is aside from the quarterly Brain MRI scans with contrast, which I have to have indefinitely.

Radiation Concerns

What I am most concerned about these days though, is just how much radiation my body is subjected to. We all know that radiation is carcinogenic ie causes Cancer. But what if you already have Cancer? What is it doing to the body then?

I tried to go a full 12 months until my next annual PET CT scan was due, but a persistent shoulder pain that would not go away over a few months panicked my GP into ordering a CT scan, just in case. I suppose he had no option but to act cautiously. But I was disappointed to only make it seven months out of the year wait for the PET. He wanted me to have the contrasting agent too with the CT, just to be safe.

The Issue

Weight Gain
Weight Gain

Alongside this recent event, I have been struggling to keep weight off. I have gained 5 kilos in 5 months!

I am a slight build naturally, normally hovering around 9 – 9.5 stone and 5ft 4inches. Now, I am bang on 10 stone. No matter what I tried to do this year to keep my weight down I have failed. I have also had trouble getting a full night’s sleep and am battling staying awake past 11pm, I am naturally a night owl. This I initially blamed on my early menopause, of which I am over two years in, due to the Chemotherapy putting my ovaries to sleep, for good. My Gynecologist says there is no hope of them reigniting. This I am resigned to, and at 45 I don’t really mind. But I know about thyroids, my sister has had Hypothyroidism thyroid, since her teens, and it has played on my mind.

We decided to check my bloods, when I say we, it is the Royal ‘we’. My GP is lovely but not really up on everything Cancer unfortunately, as I live in the countryside I don’t have any options, so I ask for these tests at my request or my Oncologists request and he helpfully signs off on them. I had my last panel of bloods done last September and all was fine. I made sure to include the full Thyroid panel too, which we also did last time.

Surprise, surprise, this time, far from normal, my thyroid is under-active! By a long margin. ‘We’ have ordered an Ultrasound on the Thyroid for a couple of week’s time too.

What is a Thyroid

What is a Thyroid
What is a Thyroid

I was keeping an eye on this fascinating bit of body kit situated at the front of the neck, as when I was going for a gazillion body scans, to see if I was worth operating on to remove the brain tumor, the radiologist discovered a couple of growths on my thyroid, which are not tumors. But because there was more important things going on for me back then, it wasn’t explored further. It’s only my vigilance, which has kept me checking my thyroid. No one else seems concerned.

Yet, I am right to be concerned. And so should anyone having PET or CT scans with radioactive iodine.

You see, the issue is a high proportion of people having radioactive iodine, innocuously called ‘contrast’, have their thyroid function destroyed. To give you some understanding of what the Thyroid does for the body, here are some facts.

Your thyroid pumps out two key hormones triiodothyronine (T3) and thyroxine (T4), which are partially composed of iodine. Here's how the gland affect your well-being, head to toe.

Your heart: Thyroid hormones influence your heart rate and help control blood flow by relaxing the muscles in the walls of your blood vessels.

Your fertility: Thyroid hormones influence your menstrual cycle. When they're out of whack, you might have irregular ovulation and periods.

Your bones: The rate at which old bone is broken down is driven by thyroid hormones; when that process speeds up, bone is destroyed faster than it can be replaced—which can lead to Osteoporosis.

Your weight: Because the thyroid regulates your metabolism (how quickly your body burns through fuel), an overactive thyroid—or hyperthyroidism—is linked to weight loss, while Hypothyroidism is linked to weight gain.

Your brain: Low thyroid levels can bring on forgetfulness, difficulty concentrating, and depression. Luckily, these symptoms tend to reverse with synthetic hormone treatment.

Your skin: When your thyroid is under-active, your body stops making and shedding skin cells at its normal pace. Cells build up, causing dry, dull-looking skin. (Hair and nail growth slow down as well.) Source

This little gland controls a lot of important functions, and needs more attention in post cancer care and stage 4 monitoring.

Radiotherapy and Thyroid Issues
Radiotherapy and Thyroid Issues

Radiotherapy and the Thyroid

Radiotherapy to the neck or head can have severe consequences for the Thyroid, with up to 50% of patients developing an under-active thyroid. Radiation destroys the Thyroid's ability to function correctly, leading to Hypothyroidism, which, in layman’s terms, is an under-active thyroid.

This is what I discovered I have, in my latest blood test.

My Radiotherapy History

In my original Breast Cancer treatment, I had 30 sessions of radiotherapy, which included my neck lymph nodes. This is fairly common, if the cancer has spread to your armpit and surrounding lymph nodes, there was no evidence for my neck lymph nodes being involved the rads were – just in case.

I also had radiosurgery on my brain after surgery, although this was laser guided and not the whole brain.

Alas, no one has ever asked me to keep a check on my thyroid, even though it a known side effect of neck and head radiation.

In the course of my research, I discovered that iodine radiation can also negatively effect the thyroid when administered in CT/PET scans and see here for further information. Which is why I opted to forgo the ‘contrast’ agent and have just a regular CT scan this week. My Doctor had my blood results showing my under-active thyroid and didn’t tell me about the known link either. Which I find disappointing but not surprising.

It seems I am on my own to protect my thyroid. And I will do so.

Why I am Most Concerned

One of the contributing factors for triggering my type of Breast Cancer, TNBC, and re-occurrence too, is obesity or sudden weight gain . And a contributing factor to many metastatic re-occurrences is also weight gain. It is critical that I get my thyroid back on track quickly, as I am fast climbing above my healthy BMI.

My Doctor won’t prescribe medication to help my Thyroid until I get the Ultrasound results back, to ensure there is not more to this than meets the eye. Which would be fair enough, ordinarily. But, due to Covid-19 the clinics are swamped and prioritising patients seen as more urgent. And I get this, I really do. So, I need to help myself, I can’t afford to wait for months until I can start medication.

What I am Currently Doing About This

What I'm Currently Doing about my Underactive Thyroid
What I'm Currently Doing about my Underactive Thyroid

I have upped my Iodine, Selenium and Zinc in an effort to try and help my thyroid (If you are currently taking medication for Hypothyroidism this may interact negatively!). I am using the 18/6 fasting diet and exercising for 8 hours per week, mostly hill walking and rebounding. I have been stable on the same weight for the past 4 weeks’ but I have not lost weight. Which would be dispiriting, if I was not aware of my under-active thyroid!

What You Can Do

If you are experiencing weight gain after cancer treatment that appears abnormal it is worth checking if you had radiotherapy to the neck or head, I only found out it was administered to my neck lymph nodes too because I asked. If I hadn’t asked I would be none the wiser. And if you did have radiotherapy to these areas or had a few PET/CT scans with radioactive iodine in the last years, you can ask your Doctor to test your blood for Thyroid issues. If you are under-active (hypothyroidism) you will most likely be prescribed synthetic hormones to regulate the Thyroid and given nutritional advice.

If you are having a few scans a year, try and seek out the lowest dose radiation machine, if possible. There are new CT scan machines available, that have the lowest dose, but most public hospitals have the older machines, so it’s worth asking the question. The best ones are normally in private clinics unfortunately because they can cost three times as much to purchase.

Speak to your Doctor about whether it is a good idea to use a contrast agent with every CT scan to help minimise your Thyroid risk. And ask them if a CT is necessary, an Ultrasound or MRI may be good enough, both of which do not contain radiation.

The preservation of your Thyroid gland should not be underestimated for your body’s optimum good health.

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