Gaining weight on T3

Just wondering if this happened to anyone else? I think it's related to my diet, I've been eating more lately, definitely more carbs. But is there possibly a link to T3 and weight gain? I've put on maybe 7lbs in the past couple months, mostly in the last month. On T4 alone (with a high TSH and low FT3) I lost 50lbs over a year.

For reference I take 10mcg T3, 100 mcg T4 (as a combined tablet split at 8am and 3pm).

My latest results were:

TSH 0,26 (0,30 - 4,20)

FT3 5,40 (3,30 - 6,00)

FT4 14,20 (7,00 - 21,10)

TPO-AK >1000,0 (0,00 - 35,00)

TRAK <0,10 (0,000 - 0,099)

18 Replies

  • Dang,

    If you've been eating more that will be why you're gaining weight. 10mcg T3 is very unlikely to cause weight gain.

  • Some people find their appetite increases on t3 (or on any meds that restore health). Are you feeling better on your current meds? When I'm not well my appetite is often a bit rubbish.

  • Yea I'm definitely feeling better. But all the food has made my IBD symptoms worse, I started eating cheese recently and I think that was the culprit. Going to stop it again.

  • I was on 20 or 30 mcg T3 only for 2 1/2 years, during which time I gained three stone or 30% of my body weight. The endoscopy were baffled by this and could offer no suggestions. Anecdotally, then maybe some sort of link. I have come to the conclusion that in my case it was because my various vitamins and minerals were at very low levels.

  • Interesting. Are you no longer on T3? Have you been able to shift the weight? I'm also working on improving my vitamins and minerals.

  • The Endos took me off T3 because they did not like my suppressed TSH! I also had raised liver enzymes which they thought was because of the T3. In fact it turned out to be because, despite taking 20 or 30 µg of T3, I was becoming increasingly hypo. When I managed to get onto a proper replacement dose of thyroxine (100 µg) I lost a stone and a half in the first three months. It then plateaued and it was not until I swapped to thyroid S that I lost another stone over about a year. I am now within half a stone of my pre-hypothyroidism weight.

  • Thyroid S is NDT correct? Have you been doing anything else to lose the weight or do you find it is completely related to whichever medication you're on? On a related question did you do better on Levo 100mcg vs the T3? And then did you find the thyroid S even better for your symptoms?

    I'm trying to fix my conversion issues by supplementing the vits/minerals that I'm deficient in. I'm hoping I can eventually switch back to Levo only since it was easier to take than having to split T3 through the day.

  • Correct. When I got to 100mcg Levothyroxine, I kick started the weight loss with a fairly strict diet for about eight weeks, but it came off slowly and steadily, whereas on T3 only it was just piling on and I could not stop it. I don't feel any better on NDT really, but I had to swap because, for some reason, my TSH is always suppressed on medication and this meant my GP was always trying to reduce my dose even though my FT4 was well within range. I got fed up with fighting with him.

  • Ah ok, thanks for sharing your experience. I think if for some reason I'm unable to shift the weight I'll give NDT a try, or possibly Levo again if I can improve my conversion.

  • Why do you split your t3? It can be taken all at once which is a lot easier. I take mine at bedtime in one dose of 80mcg.

    Jo xx

  • When I first started taking T3 I was going through swings (fast heart in the morning and tired in the afternoon), this was with 5mcg added to my T4. Eventually this settled and my Endo added another 5mcg of T3 along with more Levo.

    He said something about the immediate effects of T3 lasting around 7 hours and he's the one who came up with this schedule of me taking half in the morning and then again around 3pm. He also mentioned he has patients who take 50mcg all at once in the morning, so maybe I'm a little sensitive to it?

    The thing is it's kinda settled down now and I've been thinking of trying it all at once in the morning or at bedtime, if I were to make this change would I try it just for a day and see how it goes? Or do I need to stick to it for a while?

    Also are you on a "slow release" T3?

  • Hi, I'm not on slow realease and think that you would have to try it all in the evening for a few weeks to see if it helps. You are possibly not on enough t3 for it to last till the next night.

    Jo xx

  • Thanks for the info!

  • I found the weight gain increased as symptoms developed and grew, and when I went on t3/t4 mixed, I lost a st without even trying and then plateaued. Ended up on t3 only - as couldn't convert t4. Adrenals had been compromised. Only when meds balanced and I went to a slimming club, did I lose the weight, but I'm convinced that it was because the meds were balanced and I found it easy to lose 4st in 11 months. But when stress interferes again, find weight is affected again. With me, I found the weight gain was more likely due to t4 - as that is what I was on for 20+ years - it did me no good at all and was becoming more and more toxic with it.

    My personal theory is that, because we are so undereducated and tired all the time, our bodies are craving energy , food, but it becomes a vicious circle, as the slower our metabolism becomes, the less we are able to process food, etc to get the energy we need, and so it is stored as fat.

  • Thanks for sharing your experience. For me T4 made me lose weight without really trying, but since T3 has been added I've only been gaining

    However your point about balance and exercise makes sense. I felt like in T4 I was losing weight no matter what I ate, and now my symptoms are better and I need to watch what I eat. Maybe I'm better balanced now and like euthyroid people I gain if I eat to much and lose if I eat too little? I'm now making some diet changes hoping that will help. But I will also introduce exercise and see if this helps.

    I will also keep in mind the T4 thing because it seemed like I wasn't converting, while on T4 alone my FT4/FT3 ratio only kept going up till it was 7:1 before they finally gave me T3. Maybe the T4 part of it is still not working for me. How would you find something like that out? Do you have to test RT3? I've only ever had TSH, FT3 and FT4 tested

  • Just shows how we are all different! (Yet one treatment suppose to suit us all!!) Be careful with the exercise, I'm no expert but have read if your metabolism is not right exercise is likely to make it worse and hence add to the weight gain. To be honest, I'm not too sure if I've ever had Rt3 tested. Due some tests shortly but doubt gp/lab will be doing that one! Think they generally only do tsh and ft3/4 if that. Think would have to do private testing to get full tests done.

    It might be worth you posting the results you had again, on a separate thread, and ask about conversion. Someone better informed than I will probably be able to tell you more.

  • That's good advice, I'll make a post will my past tests up to now. I've been meaning to make a spreadsheet plotting my results anyway :)

    Thanks again for your help!

  • I did do that (Spreadsheet) with mine past results some years ago when first went to Dr P.

    Should really find it and try to update it! (Probably have to start from scratch!! -Off-putting) Good luck

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