Exercise and hypothyroidism

[Lorwri12]

I have some questions that I hope make sense and can be answered.

As mentioned in a previous post I’ve been training for a cycling event that takes place next Saturday I’ve actually pulled out because I’m not where I should be thanks to under treatment for two years.

During this past two years I’ve been not only training on the bike but also lifting in the gym to develop muscle strength. I’ve pushed very hard in both areas and now I’m struggling.

My questions are around exercise.

1) If you exercise hard are you using T3 and if so if you have T4 in your system even if it’s low does it convert to T3. Is this a slow process?

2) I’ve noticed that if I’m not super exhausted and go to the gym and push hard to lift and use weights even if I’m struggling I might sometimes be better on my bike in the afternoon. Why might that be?

3) Does having more muscle mass mean you need more T3 and T4 to be well? My GP is very concerned that I’ve had two increases in Levothyroxine and I’m concerned I may not get another even though I’m still having symptoms.

I’m 60 years old and relatively small weight is 9st 7lb and I’m 5ft 4. I’m on 125mcg of Levothyroxine. I was on 75mcg for 2 years but always only just in range for FT4 and FT3. I am/was strong and muscular. Whilst I have maintained strength I have not improved despite my best efforts this last two years.

I don’t want to give up on my cycling hobby

Thanks in advance for any advice.

[diogenes Remembering]

Your present T4 dose is 125/64 = virtually 2 mcg T4/kg body weight. For a normally fit person that is OK. Doing hard exercise increases your basal metabolic rate (BMI) so that you use the hormones more. If you have no thyroid at all, then you can only work as long as you have adequate T4 in your body. Once that falls below the acceptable, you virtually "black out" and stop because your body is out of balance. Often "just like that" with little warning. I would suggest raising T4 dose an hour or so before you do exercise, by 25. That might give you the extra push to get through.

[Lorwri12 in reply to diogenes]

Thank you. I didn’t know about taking extra T4 an hour before exercise. I’ll try that and see if it helps. I do completely shut down and one reason for pulling out of the event next week is that in training I have felt like the switch went off and I stopped!! I clearly can’t and don’t want to find myself in that position in a competitive event.

Thanks too for the reassurance about my current dose. Whilst I can say I feel better I can’t say I feel well yet. My next test is due 21st October so maybe I will by then.

[jimh111]

Looking at it a different way. Exercise raises TSH just a little, suggesting more hormone is needed, whether this is because of more T3 being 'used' at receptors or quicker turnover I don't know, guess it doesn't matter. T4 is converted to T3 in muscles (and other tissues). I don't know of any study that has found muscluar people have higher T3 levels. So, maybe just a touch more hormone is used during exercise. If I remember correctly I think there are some studies that show TSH falls a little after long term exercise. i.e. the body makes better use of its hormones. I find I get tired a hour or so after a morning's badminton, I think this may just be normal recovery not hormone related.

[Lorwri12 in reply to jimh111]

Thanks. I think there is an element of the body making good use of hormones when you exercise regularly. I’ve only ever been at the bottom of the range since diagnosis two years ago. I have cycled over a hundred miles every week and heavy lifted 3 times a week. It’s only since May this year that I’ve had real problems that said I hadn’t improved as much as expected with all my training.

I had a holiday in April/May and cycled 50 miles a day for two weeks. I was pretty exhausted everyday but still pushed myself hard. Now I think that’s when I hit problems.

I’m desperate to return to cycling properly rather than 45 minutes max which is all I can do at the minute.

I’m going to try 25 Levothyroxine an hour before exercise to see if that helps.

Thanks again