Underactive thyroid and marathons

Thyroid and running

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02/07/2010 at 15:42


I just wonder if there is anyone else out there who had been diagnosed with an underactive thyroid and taken thyroxine, who also runs marathons?

I recently trained for and ran my third marathon four weeks ago. I have had problems with my thyroid in the past but it was sub-clinically overactive and the symptoms were mainly eye problems. I noticed while training for this marathon that I was getting silly tired after long runs, complete brain fogs that took days to clear, and training and running were just so much more effort than for the last marathon I ran (last September), and I put on huge amounts of weight despite 50-60 miles/week (trust me, I haven't eaten all the pies......). Sure enough a blood test revealed an underactive thyroid and 3 weeks ago I was started on 50 mg thyroxine.

My question, has anyone else been in this situation, how long does it take for things to even out and is it possible to train and run marathons (and still get PBs)? I haven't had any improvement in the tiredness yet, but then it's still only four weeks since the marathon. But the weight is shifting, finally.....

02/07/2010 at 16:49


I suggest you go and find Crash Hamster (normally to be found loitering on the Radio Worcestershire thread on Clubhouse - although is currently away for a few days).  He's has thyroid issues and has done IM so should be able to give you some advice.

02/07/2010 at 17:16

I was going to say that.

I've been on thyroxine for a couple of years now, and it took close to 2 months before I felt the full effect of it. Don't know if you take iron tablets at all, but be sure not to take the iron and thyroxine at the same time if you do.

I've not made it up to marathon level, but set new PBs at 10k and 10 miles while on thyroxine.

02/07/2010 at 18:12

Thanks v.much, I have sent Crash Hamster a message!

I don't take iron tablets, I had that checked when I had my thyroid bloods done and it was okay. I had heard that thyroxine needs to be taken on an empty stomach, and not with iron or calcium.

To be honest I think the brain fog is actually getting worse, I'm looking forward to this stuff kicking in and getting back to some sort of normal life/training...... and weight!!

02/07/2010 at 18:52

Sally, don't worry too much about the brain fog, it'll get better the longer you're on the tablets, although you might want to treat yourself to a nice notebook and pen.

I read messages in an online support group where some people say they get up at 4am in order to have their tablets on an empty stomach and with cold water, not with juices, anything hot etc etc. My doctor is happy for me to take mine with my breakfast and mug of tea and to adjust the dose to suit my routine rather than adjusting my routine for the tablets...there's no way on earth I'm getting up at 4am to take some pills!

Which reminds me, my next blood test is on Monday.

Slowtwitcher    pirate
03/07/2010 at 06:19
I know what you're going through. I take 150ug a day. I've been taking them for about 9 months now, but still have the odd "brain fog" day. I need to be really alert and highly conversational in my job and really struggle sometimes.
03/07/2010 at 08:04


 Yeah I find the foggy head really hard to deal with too, it usually starts after lunch and stays for the rest of the day, and has made work a nightmare. The biggest problem is they all know I run long distance and I worry that they will think that's the reason I'm not performing 100%, but I'd never had that fuzzy tired feeling when training before....

Weighted myself again this a.m., another 0.8kg has just evaporated! Did you guys find you returned to your normal pre-thyroid problem weight?

 I get up and take my tablet with water, then leave brekkie until just before I go to work so it has a good hour on an empty tummy.

Fingers crossed it'll all settle down  

Edited: 03/07/2010 at 08:12
03/07/2010 at 08:12
Hi Sally, I'm on 150mcg/day and have run marathon PB's and completed two IM since being diagnosed. Still suffer with brain fog and struggle to keep my weight down though! It might take a while to get your dose right and I have found, and heard anecdotally though there doesn't seem to be a lot of evidence to support it yet, that hard training suppresses my TSH and increases my T4 - so be careful when you have your blood tests.
03/07/2010 at 08:25

Wow, that's amazing you've done two IM even without the thyroid issues, I would love to try that

I am still trying to get my head round all these T numbers, and to be honest can't really remember what my levels were but will pay more attention next time. The blood test that was taken where the consultant decided to medicate was at the start of my taper. When you say be careful, do you mean no hard training in the day/s prior to getting bloods done, or would what you've done in the weeks around it have an effect? I think I read somewhere that directly post marathon thyroid hormones are elevated!

 I have stuggled sooo hard with my weight, I was always quite slender and suddenly piled on masses for no apparent reason. I would eat very little and count every calorie, and then step on the scales at the end of the week only to discover I put weight on!? Many tears were had.

But since starting the thyroxine 3 weeks ago 2.2kg has just evaporated. Every cloud I guess.....

It's encouraging to hear it hasn't put any of you off going for it, it never crossed my mind to give up, I just wondered how hard it would be.....

03/07/2010 at 09:53

Sally - go for it! IM is within reach of anyone who wants it enough.

If I have my bloods done when I'm in a period of hard training the results are skewed - and not in my favour. I find it best to wait either until a couple of weeks into the taper or a couple of weeks after my target event. It's a good idea to note the numbers too and keep a track of what's going on - some doctors believe in running you to the 'normal' levels regardless of how you feel, others (like my current lovely GP) take note of how you feel. In the UK we treat anything up to a TSH of 5 as normal whereas in the USA they treat anything over 3 as hypo and I feel very ill if my TSH is as high as 3.

03/07/2010 at 10:22

It's on my to do list, and maybe one day I will compete in one...... first I want to run Boston

Luckily I have a Consultant Endocrinologist on my case as well as my GP as I have had sub-clinical hyper problems in the past. He seems to be a lot more switched on to what's going on and how to deal with it than my GP (and so he should I guess.....). I feel in safe hands, though none of them seems to know much about how it might affect running marathons etc. and vice versa.....

Good tip about the bloods, I'll make a note not to get them done in or around periods of heavy training. I will also make a note of my levels, and I ought to read up a bit more about it I guess as well!!

03/07/2010 at 17:51
Sally - one of the problems with reading up on hypothyroidism is that everyone has slightly different effects with some commonalities. I put on weight, get very brain foggy, lose my hair, have dry skin and muscular aches when hypo but whilst these improve on thyroxine they don't go away - nor do the palpitations and problems with muscle perfusion and recovery - but you may only experience two or three of these and be able to add an entirely different list!
05/07/2010 at 17:20

Sally i am also hypothyroid and have just ran third marathon - you are lucky with the weight loss I really struggle with mine.  I agree with LMH that a test during heavy training probably not the best idea and everyone has different symptoms.  I was on 150mcg for years but dr just increased it last week.  My results were in normal range but he agreed that it wasn;t right for me, he also suggested that as I trained even harder for my last marathon that might have upset the balance.  It took me a couple of years to get dosage right and feel ok but that is extreme most people settle down in 6 or so months.

Waves at LMUH - i was actually looking for you last week via the old thread - how are things?

05/07/2010 at 20:02

I missed it Mrs O! Was wondering how everyone was.

I'm ok - not sure if I'm going out of kilter again as my hair is falling out, I'm crackered, struggling with my weight and my brain isn't working - but as I'm in my last peak week of training there's no point going for a blood test. Will see how I feel in a couple of weeks time. How about you?

05/07/2010 at 20:18


Yeah, It is really odd isn't it how very differently people are affected. I was first diagnosed subclinical hyper a couple of years ago after my optician noticed something wrong with my eyes(Graves eye disorder), but have always had the symptoms of hypo, mainly weight gain and really frequent, heavy, incredibly painful periods. It was just over recent months that the fuzzy head and general tiredness set in.

My GP is lovely though and spotted my history and sent me for more bloods right away which showed I had done the complete cycle into hypo (my Consultant had warned that might happen, but my bloods were normal for a while so I sort of slacked off going for the tests....), and here I am now nearly four weeks on the pills....

I have lost  quite a bit of weight considering I'm not training, and last period was spookily calm, but I'm not getting symptoms of too much thyroxine so am hoping I might just be getting back to 'normal'. Have any of you ever had too much, what does that feel like?

I would love to know how the increase works for you Sarah, and it is good to know that there are other runners out there and it's not the end of the line for my marathons


05/07/2010 at 20:21

Crikey Little Miss Ultra, I didn't see that message before I posted mine, that does not sound good

 Do you have an event on the horizon then? I hope you start feeling better....


06/07/2010 at 07:29

It's pretty normal for me Sally, just varies in degree  I have a half IM on the 24th July.

Too much thyroxine can make you hyper - so much the same symptoms (possibly) apart from weight loss and trouble sleeping. Keep an eye on your RHR, it's a gross sign of hyperthyroidism but if it gets very high it's a good indicator.

06/07/2010 at 14:02

am also hypothyroid and have completed 5 marathons!

i reckon once they have the medication right that we can do anything anyone else can?!

06/07/2010 at 15:59

We sure can I did my first one untreated training was so much easier when i was taking thyroxine.

LMUH I am feeling good now I totally loved the training for VLM this year so was gutted when my running went steadily downhill in the last few months a couple of weeks ago I could barely get around 3.5 miles because of severe muscle stiffness.  For once though my Dr listened to how I felt and agreed that a tsh of 2.5 was too high for me - when this happened before he dismissed it.  It turns out that a really good friend of his has underactive thyroid and is doing an iron man so my dr is getting his head round the fact that blood test results are less of an indicator than how you feel - HURRAH I've only been telling him that for 5 years.  He also does think that heavy training can deplete your thyroxine so LMYH I am not surprised that you are a bit hypo right now.  Maybe as you ahve a nice doc she might let you up your dose?

Sallysox I do think it is harder to complete marathons when you have this, I gain fitness far more slowly compared to other people around me and lose it quicker, I also really really struggle with my weight. However that just means the achievement is greater also I am convinced that being as fit as possible helps, i reckon things would be a whole lot worse if I wasn;t so fit. 

Anyway new dosage seems to be kicking in have lost 2lbs and ran 4.5 miles today and it was easy and felt great.

06/07/2010 at 17:23
Good news Sarah! Amazing what a bit of personal insight (if slightly secondhand) can do for peoples understanding. I too think that it's still a bit harder - I definitely put on weight very easily and lose it with a lot of difficulty and am also tired a lot of the time whether training or not. Whilst my GP is lovely and will let me run very low TSH wise she does get worried when the figures (especially T4) are outside of normal limits so I don't think I'd get much joy at the minute - and it should get better when I taper. Fingers crossed!
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