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Does Levothyroxine cause atrial fibrillation?

Answered by
Dr. Ilir Sharka


Practicing since :2001

Answered : 6436 Questions

Posted on Wed, 28 Oct 2015 in General Health
Question: Hi Dr Llir

You may remember you answered some questions on my ECG and history regarding paroxysmal AF whip I thank you for.

I have had a history of ectopics and paroxysmal AF. (Normal echo) The recent cases 2013 and 2015 were cardioverted in ER. I am now taking bisoprolol 2.5mg bd with good effect

I had a recent medical and TSH was 6.2 with normal T3 and T4, repeat at 4 months demonstrated TSH at 13 and normal T3 and T4.

I have a feeling they might try leyothyroxine but am worried the drug may cause AF attacks. What' are your thoughts please?

Thanks XXXXX
Answered by Dr. Ilir Sharka 1 hour later
Brief Answer:
I would explain as follows:

Detailed Answer:

Hello again, XXXXX!

I understand your concern and would like to explain that your last TSH level (13) is pretty high accounting for your adult age.

What is a bit confusing seems the fact that T3 and T4 hormones are normal facing an increased TSH.

In fact, T3 and T4 should be abnormally decreased (if primary hypothyroidism, like for example Hashimoto’s thyroiditis would be the cause), or increased (if a thyroid hormone resistance or a pituitary adenoma would be present).

So suspicions are raised about the accuracy of the tests. Other exogenous factors may have influenced those results.

I recommend confirming the accuracy of the test with your endocrinologist.

Could you upload the full result of TSH, T3, T4 tests for a direct review?

Regarding the fear about new AF bouts, I would explain that if clinical hypothyroidism is confirmed, a concomitant starting of L-Thyroxine should be accompanied by an adequate dosing of a beta-blocker, such as Bisoprolol or any other equivalent.

In such case, the risk of over-triggering catecholaminergic response would be controlled.

So, relax and don’t worry about!

You just need to discuss the above mentioned issues with your attending doctor.

Hope to have been helpful to you!

If you have further uncertainties, feel free to contact me!

Kind regards,

Dr. Iliri

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
Follow up: Dr. Ilir Sharka 4 minutes later
Thanks. I have not received the results on paper yet but on both occasions the TSH was raised. Is this not subclinical hypothyroidism where TSH is high and T3 and T4 normal. I am already on 2.5mg bisoprolol bd - Is it worth considering increasing this if I do end up on leyothyroxine to maybe total of 7.5mg od? Thanks XXXX
Answered by Dr. Ilir Sharka 11 minutes later
Brief Answer:
Beta-blocker dosing will be guided after a close cardiovascular monitoring.

Detailed Answer:

Dear XXXX,

As I explained you before, it is a bit strange that your T3 and T4 levels have remained normal, despite an important increase of TSH level.

Probably it would be the case of a subclinical hypothyroidism, though with such a high TSH level, a clear hypothyroidism would be likely (if underlying clinical symptomatology is revealed).

I recommend you to consult with your endocrinologist about a complete review of your symptomatology and lab tests.

Regarding Bisoprolol, dose increase may range up to 10 mg/day. But, this will depend on the L-Thyroxine starting dose and the subsequent cardiovascular response.


Dr. Iliri
Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
Follow up: Dr. Ilir Sharka 3 minutes later
Thanks for the advice
Answered by Dr. Ilir Sharka 4 minutes later
Brief Answer:
You are welcome!

Detailed Answer:

I am at your disposal, if you have further uncertainties!

Best wishes,

Dr. Iliri

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

The User accepted the expert's answer

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