Prevalence of abnormal thyroid hormone levels in acute new-onset atrial fibrillation

[helvella]

One of the most common heart/thyroid assumptions - thrown at thyroid patents everywhere - is that atrial fibrillation is almost certainly related to hyperthyroidism or over-medication with thyroid hormones and is a symptom of some form of thyrotoxicosis.

Some, quite a few, stalwarts here have repeatedly pointed out that is fundamentally untrue.

Personally, I have found that too little levothyroxine sees my permanent atrial fibrillation worsen considerably. While I always have afib, the rate goes up if I am under-medicated. And, as one bit of evidence, my smart watch keeps telling me it is too high. (Of course, I can choose the level at which it warns.)

Now, at long last, we have a paper with a conclusion:

This study found that subclinical hypothyroidism was more prevalent (4.9%) than thyrotoxicosis (1.2%) among patients presenting with acute NOAF.

They then admit hypothyroidism plays a more significant role than thyrotoxicosis.

I get the feeling that this has been a bit of a surprise to them. But not to quite a few of us!

Prevalence of abnormal thyroid hormone levels in acute new-onset atrial fibrillation

Abstract

Introduction: Known risk factors for new-onset atrial fibrillation/flutter (NOAF) include thyrotoxicosis and subclinical hypothyroidism. While prior research has predominantly explored the link between thyrotoxicosis and NOAF, the presence of subclinical hypothyroidism among patients presenting with acute NOAF in the emergency department (ED) remains an underexplored area of inquiry. This study aimed to assess the prevalence of undiagnosed thyrotoxicosis and subclinical hypothyroidism in patients with acute NOAF diagnosed in the ED.

Methods: This registry-based cohort study was conducted in the ED at Vrinnevi Hospital in Sweden during the years 2018, 2020, and 2022, with a 1-year follow-up period. Patients ≥18 years diagnosed with NOAF in the ED, with no ongoing thyroid hormone substitution or previous documented thyroid abnormality within the past 2 years, were included. The primary outcome was the diagnosis of thyrotoxicosis or subclinical hypothyroidism either in the ED or during a 1-year follow-up period.

Results: 486 patients with NOAF were included in the study (43.6% females). 329 (67.7%) underwent thyroid function testing in the ED or by the end of the 1-year follow-up. In total, 16 (4.9%) patients presented with subclinical hypothyroidism while 4 (1.2%) patients presented with clinical or subclinical thyrotoxicosis.

Discussion: This study found that subclinical hypothyroidism was more prevalent (4.9%) than thyrotoxicosis (1.2%) among patients presenting with acute NOAF. These findings contrast with previous research that has predominantly linked thyrotoxicosis with acute NOAF, suggesting the need for further studies including both subclinical hypothyroidism and thyrotoxicosis in patients with NOAF.

Keywords: acute new-onset atrial fibrillation; atrial fibrillation; emergency department; hyperthyroidism; subclinical hypothyroidism; thyroid testing; thyrotoxicosis.

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Conclusion

In conclusion, subclinical hypothyroidism was more frequently prevalent than thyrotoxicosis (4.9% vs. 1.2%) in patients diagnosed with acute NOAF, suggesting it may play a more significant role than previously recognized. These findings suggest that there is a need for further studies including both thyrotoxicosis as well as subclinical hypothyroidism in acute NOAF and further research into the clinical implications of subclinical hypothyroidism in this population.

Open access:

frontiersin.org/journals/ca...

[FallingInReverse]

This deserves to be pinned!

[Staffsgirl]

Great!

[helvella Administrator]

(4.9% vs. 1.2%)

That works out as a more than 4:1 ratio of hypothyroid to thyrotoxic. Much, much more likely to be hypothyroid - over the population.

[Easylover in reply to helvella]

I like the way you spelled it out...4:1. It's huge. Thank you.

[JGBH]

Thank you so much for this important information. However, how are we going to convince all the ignorant medics? I have just been diagnosed with AFib… am so worried because I feel so ill, very weak, permanently exhausted and no energy whatsoever. I have a combination treatment, thyroxine and Liothyronine, so I wonder whether Liothyronine is going to be blamed for my diagnosis…. as is always the case. Liothyronine was prescribed by an enlightened endocrinologist.

[TSH110 in reply to JGBH]

Oh yes it will be, like my NDT was, they told me to stop taking it 😳 I said “What? and DIE?” This is the total ignorance we are up against

[JGBH in reply to TSH110]

So what are you tanking now if they have stopped your NDT. Who stopped it, a GP, a cardiologist or an endocrinologist?

[jgelliss]

Yes! Yes!Yes! It happened to me especially when my heart was not getting enough T3 from my T4. Helvella Thank You for bringing Great and Informative Vital Posts for our Great Forum. Years ago when I was experiencing these awful symptoms I was in a panic mood because no Dr ever figured it out. One Dr even told me not to think about it. As if thinking about it would bring it on.

[Easylover in reply to jgelliss]

I'm sorry but I laughed when I read your doctor told you not to think about it. It's so funny to me. ☺

[jgelliss in reply to Easylover]

And truth be told he was a brilliant thyroid surgeon in a very prestigious hospital. I at first didn't think I heard well. And asked him to repeat it. Trust me back then all I wanted to do was cry. As if it was my doing. That's how little Dr's and thyroid surgeons understood anything about T3.Glad you had a good laugh. Today I would also laugh.

😆

[Easylover in reply to jgelliss]

I'm sorry for all the drama we go through as thyroid patients. I didn't mean to laugh. There's really nothing funny about pain n suffering. I'm sorry for all the stuff you went through. Thank you so much for sharing your experience with me. Truly, it matters. I have cried too friend.

[jgelliss in reply to Easylover]

It's a very tragic journey when Dr's have no idea how to dose us . I often say we need Dr's that Listen to patients and Think Out Of The Box. And dose by symptoms and not just lab results. Wouldn't that be a more perfect way to go????

[Pearlteapot]

I don't have AFib but I did get palpitations for the first time in my life while undermedicated on Levo alone. The thyroid consultant advised that I was over-medicated when all the other symptoms pointed to quite severe under-medication. The palpitations caused by under -medication would have led to me being kept in an undermedicated state, in a cycle of doom. I had read many posts in this forum that suggested that the converse may be true so I insisted on an increase. Palpitations then stopped.

[helvella Administrator in reply to Pearlteapot]

Glad you had read sufficiently to stand your ground.

[Pearlteapot]

Included within what I read was material about cardiologists using T3 to help the heart after cardiac events. Heart needs T3.

[jgelliss in reply to Pearlteapot]

Yes!!!! Wish you can hear me Shout. Muscles need T3 and the Heart is a Muscle. Cells, Brain, every part of us depends on T3. What part don't Dr's Understand????

[imogen2010]

brilliant informative information.. under medicated for me is just how that feels why can’t these doctors listen to us & how our body’s feel 🥲

[jgelliss in reply to imogen2010]

Totally Agree.You think if Dr's would get kick backs from T3 manufacturers they would prescribe T3 more readily????

[thyr01d]

Very interesting, thank you

[Easylover]

I'm so frustrated with doctors that I don't want to go back. I just prefer to believe there is one out there for me who is open to the truth, one who cares about how I feel, what I want.