To keep a long story short, I'm pretty sure I developed subclinical hypothyroidism a couple of years ago. I was exercising fairly hard during this period (with fell running) and was feeling more and more tired than usual but pressed on with training anyway. Ended up having pretty bad attack of arrythmia while in the hills and was finally diagnosed with atrial fibrillation last December. I suspect that overexercising was the culprit, but my cardiologist doesn't think the underactive thyroid had anything to do with it.
Does anyone have any info on strenuous exercise while hypo causing heart problems? Thanks.
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Barny12
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It makes me want to weep that a cardiologist would not realize that low thyroid levels would compromise the working of the heart. I cannot point you in the direction of any studies but I am sure someone will and in the meantime, perhaps you could post your actual thyroid blood test results at that time. I assume your cardiologist checked these?
Hah! The cardiologist didn't even ask about my thyroid until I mentioned possibly being hypo and even then didn't enquire as to my blood test results. I'll post my bloods in my reply to SlowDragon. Thanks.
First step is to get FULL Thyroid and vitamin testing
Low FT3 is extremely common when under medicated
How much Levothyroxine are you currently taking?
How long at that dose
Do you always get same brand of Levothyroxine
Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .
Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)
Is this how you do your tests?
Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or all vitamins
Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random
If antibodies are high this is Hashimoto's, (also known by medics here in UK more commonly as autoimmune thyroid disease).
About 90% of all primary hypothyroidism in Uk is due to Hashimoto's.
Have you had thyroid antibodies tested already?
Or vitamins?
Low FT3 can affect the heart
Marz has link to book on heart and its close links to thyroid hormones
Come back with new post once you get full Thyroid and vitamin results
Thanks for the reply. I didn't get the full bloods done at the time, just the basic NHS one. (TSH 5.92, T4 10.60 I was just hoping for some idea of how realistic a concept it might be that strenuous exercise while hypo may cause heart problems. Thanks.
Those readings were from bloods taken when I was being checked for afib. I self diagnosed that as I was vegan I was likely to be iodine deficient so began an iodine supplement from the Vegan Society. My following 3 monthly readings were TSH 2.82 T4 10.8, then TSH 2.32 T4 9.10, then TSH 2.775 T4 9.90.
My GP advised no further treatment for thyroid issues, so my main focus has been the atrial fibrillation.
Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .
Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)
If/when also on T3, make sure to take last dose 8-12 hours prior to test, even if this means adjusting time or splitting of dose day before test
Is this how you do your tests?
Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or all vitamins
Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random
Thyroid hormones that are too high, or too low can cause AFib. Cardiologists are supposed to investigate possible reversible causes of AFib first- haha. (See NICE guidance) AFib can also be triggered by exercise if you are prone to it.
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Hypothyroid and exercise
Hypothyroidism and exercise
Hypothyroidism & exercise 
defining strenuous!
