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Thyroid UK
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Hypothyroidism and exercise

I keep reading that anything classed as more intense than 'moderate' exercise depletes T3 at a rate of knots; for euthyroid folks this isn't a problem as the feedback loop kicks in and their bodies produce more to compensate but for those of us reliant on taking hormones by mouth this isn't an option. (And I can attest that since taking up running my thyroid levels have been all over the shop, but mostly down.)

Therefore on days when I go running is it feasible to take just that little bit more hormone (either T3 alone or more levo) to cover it, or would I need an increased dose every day? Has anybody tried this? Giving up running isn't an option I'd like to consider as it's done wonders for my mental health and I'd like to come off the lithium sometime in the next year.

8 Replies

Hi hose. I'm not as knowledgeable as others folks here, so I can't answer your question, but I can completely empathise with how you feel about running. Since I started running in 2011, it has had numerous benefits for both my physical and mental well-being, but my running is now being hampered by what appears to be a thyroid problem. I currently get breathless just walking up the stairs, let alone trying to run, but am getting nowhere with getting the problem diagnosed. Given that I finally started losing a stubborn few stone due to taking up running, before the breathing problem started, I certainly don't see that giving up such a healthy, enjoyable hobby can be good for anyone. I didn't run for a couple of weeks over Christmas, and my first run (a very slow 5K) went well, with almost no breathing issues. However, now I'm trying to run 2-3 times per week again, I'm finding it impossible to breathe from the outset. :-( Therefore, it does sound like my T3 is getting depleted, as you say. I want to be able to run (and train to improve) more than once every fortnight! I'd love to know the answer to you question too. Happy running. :-)


I take an additional 5mcg after my cardiac rehab (managed exercise) session.

It made a significant, positive difference.

levo is slow-acting, so I doubt that this will have a noticeable impact, whereas T3 works in a few hours.


This is so interesting and explains a lot of the issues I've been having with excercising in the past few months. I had no idea T3 could help. I started to get a bit worried at having to stop mid-shred. Just started HIIT treadmill workouts which seems to be easier than constant speed/activity. Will start taking 5mcg after my workout and see if it helps. Thanks very much!


This is really interesting! I assumed my breathlessness whilst running was down to me getting older rather than my thyroid issue (Im under active, diagnosed 4 years ago when I gave up smoking). My chest feels so tights sometimes, I really struggle to get the breath in. I will keep persevering though, because as you say hose, it helps with your mental health as well as physical.

Im so pleased I have found this forum, I knew nothing of T3 and T4 and their differences (just read a really good post by Clutter). I had heard about the benefits of Vit B and Vit D, but that was following a search into St Johns Wort as I have mild anxiety issues. Although I take 75mcg of levo daily, there are times when it seems to make no difference at all. I always take it in the morning (have tried night time but I went downhill), and dont eat breakfast for another hour. I still have symptoms I cant shift (itchy skin, IBS and bouts of brain fog are the ones I most dislike!!)

Seriously there have been times I thought I was going mad, Ive felt so ill and low. So thanks everyone. I dont feel like Im just whinging for nothing now.


It's also worth noting that breathlessness can be caused by B12 deficiency, which I've also discovered I have (it and thyroid problems are often connected). I'm taking 50mcg levo and 10,000mcg B12 daily at present, but I am still suffering breathlessness, just not quite as much as before. I'm not yet sure whether I need more levo or B12 injections or something else to finally clear this up. The running is really suffering at present. :-(


Thanks for replying Legion.

I started on B12 today and am going to keep my fingers crossed for some improvement. Its all such a minefield. It seems to be just a case of trial and error, and finding a way that works for you.

I do wish doctors were more responsive to the fact that this has such a massive impact on everything though. I've felt like such a hypochondriac for years, but at least by finding this site, I feel I can take more control by being more informed

I really hope you find what works for you soon

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I hope it helps. Let us know how you get on.


Does your doc trust you enough to give you a higher dose and let you change it according to your needs?

Your prescription is officially written for your "high output" days, and you just split your pills on normal days.


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