Under active thyroid : I am currently taking... - AF Association

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Under active thyroid

Jeanette49 profile image

I am currently taking only Apixaban for PAF, had an ablation 2 years ago, and just occasionally get bouts of ectopics, never a rapid heartbeat. My issues have only ever been ectopics, very very rarely going above 100 bpm and only for brief periods, nothing worth noting really.

My thyroid function has slowly been deteriorating over the years, it runs in the family unfortunately. Nearly at the point of needing meds, but the doctor is reluctant because of the heart issue, she said they will have an adverse effect!

It would be nice to hear of others’ experiences please x

35 Replies

If your thyroid function is inadequate, it will have adverse effects and not only on AF.



Who knows your underactive thyroid could be the cause of your ectopic beats! I have AF and an underactive thyroid and taking a small amount 75mg of Levothyroxine has given me back my life.

When we have AF, GP's generally start us on a very low dose 25mg of Levo and increase it 6 weekly until your thyroid function is normal. My taking it didn't affect my heart rate in any way, in fact it may have made it better.

I would want to give it a try.


Thanks Jean, that has helped me a lot, I’m not quite so apprehensive now, my bloods have been gradually creeping up for the last few years, and nearly to the upper range now.

Next tests in six months then a decision will be made as to whether I will start meds.

When you say "creeping up" what was your last TSH test result?

I'm on 125mcg Levo a day and now 20mcg T3 a day, about to increase that one as still hopelessly under medicated by the feel of it. Blood results should confirm that on Monday.

I have persistent AF with high heart rate (for me) of in the 90's with a beta blocker. When I first added some T3 to my thyroid meds my HR dropped to the 80's. Now that I need a dose increase (I think - bloods will confirm) it's gone back up into the 90's. I'm convinced this AF is related to a low T3 level.

Hylda2 profile image
Hylda2 in reply to jeanjeannie50

Agree with Jean and I’m on 125mg of Levo. No problems

Jeanette49 profile image
Jeanette49 in reply to Hylda2

Thanks Hylda, you and Jean have helped a lot, bless you both 😘

Are you taking 75 mg or 75 micrograms?

Well spotted Jim, it should say micrograms

If a conventional doctor ever wants to kill your thyroid with radiation .... please consult with a Naturopathic doctor first. They have many effective thyroid treatments for even the worst cases .... but they can do nothing if the thyroid has already been destroyed.

I had continuous ectopics that drove me crazy after one of my ablations. Doctors said it's benign and to ignore it. Wrong answer.

I discovered a triple magnesium formula (there are many that will work) that stopped the ectopics within a week never to return. Took 400mg twice a day. Might not work for everyone, but worth a try. Good Luck!

I have taken chelated magnesium 400 mg twice a day before the ablation and have continued after. I also take Ubiquinol 300 mg per day as advised by a cardiologist. I don’t know if it’s the supplements that keep my heart rhythm stable (mostly) or the ablation to be honest, but I don’t want to risk stopping to find out.

What is the triple formula magnesium you use?

Please share which triple magnesium brand? Will try anything that helps ectopics.

Kmm96 profile image
Kmm96 in reply to Dana101

Triple calm is the best for me

Triple calm mag is the best

I used SWANSON Vitamins Triple Magnesium formula. I believe they sell online worldwide. However, magnesium comes in a dozen types, so you can mix and match .... or try other triple formulas out there. I hope you have great success!

Thank you, I’ve just ordered triple calm magnesium that Kmm96 uses, I’ll try that and see how I go. At the moment I use Solgar chelated Magnesium 400 twice a day and Solgar Taurine 500 mg once a day. I do still get occasional periods of ectopics which are fairly short lived, but I still find them very distressing and maybe a new combination will hopefully knock it on the head fingers crossed. I’ll check out the Swanson ones too. I find most of the best supplements come from America, so shipping can be expensive, as I live in Spain.

Good Luck! with it. Hoping that's the 'one' that does away with them for good. I buy lots of products from abroad ... many with amazing low shipping rates. How they do it, I have no clue.

The only thing I can add is that when I was diagnosed with an overactive thyroid, the Endocrinologist said it was important to have it treatment because it could contribute to my AF. The treatment given was radioactive iodine therapy which could cause my thyroid to become under active but he said this was easier to manage and therefore less likely to affect my AF. My EP agreed so I proceeded and so far my thyroid is in range so no medication is necessary.....

FJ is your AF or general health any better through having that done?

The only thing I’m aware of is that I generally feel calmer than before although I’m not sure Mrs FJ would agree. I did have one AF episode since it was done but that was just after my 2nd jab, it only lasted about 45 mins after taking a PiP. Energy levels haven’t changed but as we all know, getting older makes it more difficult to determine causes for general health changes.

Jeanette49 profile image
Jeanette49 in reply to FlapJack

Flapjack, I had a run of ectopics after my first Pfizer, started fairly quickly after it, and lasted a couple of hours. Same again with my second jab, my heart started bouncing around when I was waiting the compulsory 15 mins in case of allergic reaction etc. By the time I got home it was in full swing and uncomfortable, after an hour I took a PiP and an hour or so later the ectopics subsided. It was the only reaction I had to the vaccine. Been fine ever since except for one or two tiny incidents thank goodness.

As my thyroid is close to getting classified as under active, there’s not much choice as far as I know but to take meds to bring it into a normal range.

I can only say what I was told by my Endocrinologist. Medication used for treating overactive thyroid could have an adverse affect on folk with AF if taken long term whereas medication for under active thyroid is a hormone replacement and therefore benign. I’m no medic so I have no personal knowledge but from what we hear, it is important that AF patients do what they can to get their thyroid in range.

I had an overactive thyroid in my youth that was kept under control by medication and eventually sorted itself out. Then about 5 or 6 years ago I was diagnosed with under active thyroid for which I take 150 micrograms of levothyroxin. I came down with PAF a while afterwards.

I had my 1st cryoablation in April and apart from a "wee wobbler" a week or so after, it's been all good. Some doctors connected the thyroid thing with the AF thing and others don't. But for your general wellbeing I would recommend treatment for your thyroid function as leaving it causes a whole other list of possible problems I'm can assure you.

Well your doctor is the usual clueless GP who knows nothing useful about thyroid! Idiot. You may well have your heart issues because your thyroid T3 level is too low. I was about to post the Canadian Thyroid Patients resource, but baba beat me to it below.

We can have AF and other rhythm issues if our Free T3 is too low as well as too high. We also see an increase in AF in people with high Free T4 but relatively low T3.

I don't know how you are going to tackle this. Leaving it will make everything worse. Can you see another doctor? One who perhaps took the Hippocratic oath seriously? I'm not being facetious, it's just we see this kind of dangerous GP reaction so often over on the Thyroid Health board. Even endocrinologists don't understand thyroid conditions. Some cardiologists do. Mine hadn't got a clue and simply frightened me half to death at the start. Fortunately for me I already knew way more than him and I know a lot more now.

FancyPants, I’ve just checked the results that I have to hand:

March 2017

TSH - 7.428

T4 free - 0.95

Nov 2017

TSH - 5.678

T4 free - 1.03

Feb 2018:

TSH - 8.517

T4 free - 1.14

Mar 2019:

TSH - 9.965

T4 free - 0.99

Oct 2019:

TSH - 8.638

T4 free - 1.2

May 2021:

TSH - 9.307

T4 free - 0.99

This all means very little to me as far as ratios are concerned if that’s the right terminology. The results seem a bit all over the place though.

The doctor has always said that because the T4 free was always low that she isn’t too concerned about the other one! I live in Spain by the way, and their normal range is 0.55-4.78 for TSH and 0.71-1.85 for T4

I also understand that an underactive thyroid can cause liver issues, which have also come to light after a recent ultrasound.

Oh dear! You are very hypothyroid. Look at those TSH results. They should be around 2 in a healthy person. Often much less. Your GP knows nothing if she's said having a low FT4 is good! It's the very opposite of good. You need to see someone else and fast. Your body is going to be suffering for this prolonged reduction in vital hormone.

Results do flex all the time for many of us. It can be because of an autoimmune cause of thyroid deficiency called Hashimoto's, which is proven by raised thyroid antibodies but you haven't been tested. However the treatment is the same, Levothyroxine.

You do need to get your blood tests scheduled for first thing in the morning, before 9am and only drink water beforehand. No food or other drinks until afterwards. This way you get tested when the TSH is high at the start of the day and you have a benchmark to compare your future tests with. This applies when you are taking Levothyroxine too. You take your last dose 24hrs before the test and take the next dose after the blood draw. Doctors don't know this. But patients do.

With TSH results like yours your doctor is keeping you sick. I'm amazed you are able to have any kind of life. Please see someone else urgently.

Just to add, you have been hypothyroid and in need of medication since the first test in 2017 and probably before.

It seems that both my GP and cardiologist are reluctant to start medication because of the PAF! I saw the cardiologist a few days ago and she said review in 6 months, and that medication could adversely affect the heart issues. I rarely have had a rapid heartbeat, it’s the ectopics that I have mostly suffered from, and had a Cryoablation two and a half years ago, which seems to have worked, but I also take magnesium and Ubiquinol for the heart, so not sure which is being effective really - too apprehensive to stop the supplements to find out ! Perhaps they have a different approach in Spain. The blood tests are always done at 8 am after fasting, so must be accurate.

FP54 are you a medic, or is your amazing knowledge from having this condition yourself?

bantam12 profile image
bantam12 in reply to Jeanette49

Ectopics are caused or made worse because you are hypothyroid ! Neither your GP or Cardiologist are doing you any favours by denying you thyroxine.

I'm not a medic. I'm a thyroid patient with 8-9 years of hard struggle and a GP who says there's nothing wrong with my thyroid despite being positive for the Dio2 gene defect.

I have been learning about hormones for a long time. Everything is linked so I've learnt about leptin and insulin resistance, that led to thyroid and that was later confirmed and now menopause too. I won't wait for useless GPs. I have enough money to pay for some private help. I'm not rich, I just have enough to allow me to do this. So I use them to help me confirm and treat things. My PAF started just before my thyroid started to show up an issue. And the thyroid became an issue at the same time as menopause, because they are linked.

Your cardiologist is just as clueless as your GP. They often are. Mine is. He tried to frighten me off using T3 when my AF became persistent. I was taking a tiny bit. I was vulnerable at the time, from fear and let him scare me and so I stopped it. Now I realise I wasn't on enough. My last review with him was by phone and he spent most of it quizzing me about T3 and the Dio2 gene! He was picking my brains for his own benefit. He seems to have left the hospital now. God knows what the new one will be like.

Arrhythmia is caused by insufficient T3 as well as too much. But for some reason most doctors don't know about the insufficient end. If your doctor leaves you hypothyroid for years you will just get worse and more and more symptoms as your body gives up the struggle. You have to fight for this now. Tell them you appreciate their concerns but that you simply must have thyroid treatment to bring your TSH down to 1 or below. Tell them you will monitor yourself (and if you don't have one get a BP and HR monitor and do it twice a week like clockwork and keep a spreadsheet.

These doctors seem to want us to remain sick. It's not right.

I have a BP monitor which shows heart rate too. How is that related to the thyroid issue? Sorry I’m completely clueless…My BP can get as low as 90-100/ 65-70 sometimes.

Oh dear. You have relied on your doctors haven't you? That's a shame. My recommendation would be to start learning about your hypothyroidism and quickly. A good primer book available on Amazon is Your Thyroid and How to Keep it Healthy by Barry Durrant-Peatfield. A lovely doctor, hounded by the GMC and now retired due to great age. It's not complicated and it's not huge and you can skip all the stuff about hypERthyroid as it doesn't apply to you.

BP and HR are in part controlled by thyroid. We have 2 main thyroid hormones. T3 and T4. We measure free T3 and free T4 in the blood to assess how well our medications are working. If our free T3 gets too high, the top of the reference range or over it, our HR can increase and our BP too. But also if our free T3 drops too low we can have HR increases, which seems beyond a GP to understand. So if we are monitoring for ourselves we would keep a record of how much medication we are on and what those vital signs are. For me, right now, I need a dose increase in T3. My HR has risen, BP is up a bit but still normal, just up for me. Others also measure and record temperature, but I don't bother as I run on a low temperature anyway. I am rarely above 36C. Your BP is going a bit too low at times, but it will be different reasons as you are not treated for your thyroid yet. I'm 58 now, I aim for my BP to be between 100-140/85 or less. Normally it's good. But when I'm as tired as I am now it starts to creep up.

Print off the symptom check list on the link below and fill it in and take it with you when you go to your doctor to be forceful about getting treatment.


Out of interest, when you have ticked off all the symptoms that apply to you, how many don't you have?

bantam12 profile image
bantam12 in reply to Jeanette49

Just want to second what Fancypants has said, you are very hypothyroid and should have been put on Levothyroxine a long time ago. You need to change your Dr and start treatment asap !

Under active means hypo which is the opposite of what causes fast heart rhythms. Hyper (overactive thyroid) is whats known to cause AFIB and other types of heart issues. If your TSH is high (not enough T4) then you will need to start Levothyroxine, millions of people in the US have been taking this synthetic form of what your thyroid gland produces naturally. Are your seeing a good endocrinologist? I just saw mine at the Mayo Clinic last week and had this very same discussion.

FancyPants54 profile image
FancyPants54 in reply to Kmm96

In part you are correct, but not in full. Under active thyroid, with low free T3 also causes fast heart rate and AF in some people. It's well referenced out there, but not as frequently as the more normal higher levels giving fast heart rate. It doesn't even need the FT3 to be under the range, just consistently low in range for a period of time, wearing the body out bit by bit, will do it.

Kmm96 profile image
Kmm96 in reply to FancyPants54

Good to know, thanks!

🙄🙄 I had a patient who was given higher and higher doses of antidepressants for her problems but failed to check her thyroid levels 😡😡

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