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Thyroid UK
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Feel worse after exercise - indication of poor conversion to t3?

Hi all!

Following on from my last post about myself, I've got a doctor's appointment Monday to discuss increasing my current treatment (75mcg levo). However I've noticed another symptom this week and think I've read about it somewhere before so hoping someone can direct me to literature!

I've been stupidly fatigued/tired and slow to get going recently, but have still tried to exercise. I have been doing yoga on a Monday and then aerial hoop on a Tuesday for a couple of weeks, and I also cycle to work. Last week I wasn't too bad, but this week I cycled two days to work, did 1HR15 of yoga, 1 HR of aerial hoop and then a gentle swim yesterday. I'm absolutely exhausted and my body is totally crashing today.

I think I've read somewhere that feeling worse on exercise if you're hypothyroid is an indicator of poor conversion to t3 - can anyone direct me to where I might have read that? Especially if it's a journal article!

Thank you :)

3 Replies


Indicators of poor conversion are low TSH, high FT4 and low FT3.

Exercise depletes T3 which is why recovery from exercise can take 2-3 days if you have low FT3.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

1 like

queenmabroo Having a quick look at your last post, although you say you haven't had any recent vitamin and mineral tests your B12 is low but you say you're not supplementing and you are supplementing a low Vit D. You really need up to date tests, along with FT3. You won't know if your conversion of T4 to T3 is poor unless you know your current levels.

I don't think it's so much a case that feeling worse on exercise if you're hypothyroid is an indicator of poor conversion to T3, I think it's more what Clutter says ie exercise depletes T3. Maybe you should ease up on the exercise until you get the relevant tests. Once you've got these test results you can look at properly supplementing any deficiencies and see whether your thyroid meds need adjusting.


Gentle yoga can be helpful for thyroid, but too much exercise uses up all your precious T3, I'd drop the other forms of exercise (obviously if you need to cycle to work, you have to do that) until your FT3 is up the top of the range and then reintroduce it gradually.


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