Thyroid UK
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I wondered if there was any reasearch on exercise and improving conversion; as in actual data before and after a length of time on the same dose of t4 seeing t3 levels improve?

Completely anecdotally but I have wondered if I have experienced improvement through aerobic and anaerobic exercise, as long as t4 is a good level.

Just a thought!

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I found this regarding an enzyme which is involved in the process but not sure how reliable the site is?


If you exercise you use up T3


Hello again Haggisplant

This is a very interesting thought you have had. I am much, much better sometimes after working in the garden for several hours or a long walk with daughter's dog. I'd put it down to fresh air but wonder if you are onto something very valuable.


Hi haggisplant, I know I've only skimmed through this, but I can't see where it says exercise increases conversion. However, it does say this :


It has been shown that women or men who perform more than moderate exercise, especially when associated with dieting, have reduced T4 to T3 conversion and increase reverse T3, counteracting many of the positive effects of exercise in women including weight loss (236,237). Consequently, T3 and reverse T3 levels should be evaluated in individuals who exercise and/or diet to better determine cellular thyroid levels, as TSH and T4 would not necessarily reflect tissue levels in such patients."

Plus the fact that exercising uses up your T3 - and all the other hormones, come to that - you're going to end up pretty hypo, it seems to me.


It's an interesting thought. I felt much better on holiday when I was walking everyday. Maybe it was just being somewhere different and being in a "holiday" mood though? I do try to do Yoga and some walking and gardening every week, but I don't know how much of feeling better is due to just being out and about more? MariLiz


Personally I've in the past been better when exercising well and particularly using muscles as well as some aerobic stuff, plus yoga too.

I noticed it said about the enzymes being increased which help conversion.

I'd guess it was a very slow process to build everything up.


Reflecting on comments it seems pretty silly to me NOT to exercise. T3 gets used up even if you don't have a thyroid issue. Yes; no thyroid means no immediate t3 it might produce but if on the right level of t4 that shouldn't be a huge issue; justesns perhaps you need to pace and rest more post exercise. Graded excercise.

The point is though, the more you do, the fitter your heart muscle gets, the more efficient your metabolism, but I feel most importantly, the more muscles you have. More muscle = more strength, stamina, less pain as joints are supported. More oxygen to muscles. More serotonin to brain.

Not excercising to loose weight, probably the opposite, exercising to get stronger and better at things.

I had this disease so young I never knew any different and tried so hard to keep up with my peers - I got into martial arts, swimming, yoga, and started skipping to increase my cardio stamina. When under replaced, no, it was bad and I was terribly frustrated. However when correctly replaced I slowly paced and built up (in a way attending classes and a very sociable class meant I never stopped so restarting wasn't hard).

It's been having a child that's really buggered it all up in more ways than one, but one of these has been the inability to get to classes and swimming etc. meaning the climb back has been much worse. But I naturally do not hold much weight.

I saw what it said about using up t3 - as in anyone - but it noted that dionase enzyme was increased, one that improves t4 to t3 conversion.

Also, in my mind, the fitter you are to start with or maintaining, the less impact a dose blip / illness / change in meds might have.

The other reason I asked is that when I was marathon level fit I needed very slightly less thyroxine for that period. But I know I was on TEVA and it was just before the bad batch so I don't know if that's relevant (ie their brand actually went too high for a bit).

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Interesting reading. I know that exercise works for me, not just for general fitness and disease prevention (which are reasons enough to exercise), but for weight loss. I wonder if some people have problems making dionase, and for those people the rt3 generated by excercise becomes a problem, but if you do not have that problem then excercise works well?

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