Does T4 cause weight gain??

Hi everyone, thankyou in advance for your replies.

I have been taking T4 for about 7 years now i was finally diagnosed when i was 17/18. Since then my weight despite my constant dieting has continued to increase. I was a healthy size 12 now im a size 18 and have gained 3 and a half stone in weight. Ive read various articles about t4 causing weight gain if it turns t4 into reverse t3. Is this true? and if so does anyone have any information about how to stop this?

I look forward to see what you guys have to say, thankyou.

104 Replies

1) Your weight gain maybe related to under medication, and so not enough T4 is being consumed to keep metabolic rate at the correct level.

2) Weight gain can be related to the T4 itself and Dr Blanchard noticed this in some of his patients. He felt the T4 was stimulating the stomach hormones to demand more food. So over time patients would unconsciously be eating more.

His solution was to have the patients take the T4 WITH their food. I can't remember fully, but i think it was with the main meal in the evening. His book is a good read called Functional thyroid on amazon.

Thats great thanks i may have to try and find that book! I take 100 t4 and 50t3 and last time i got tested which was a few months ago now, they said my TSH levels were normal?

I heard low calorie diets are no good and ive been doing this for a long long time and got bigger and bigger throughout. Could this be it?

Thankyou for your kind reply :)

100 T4 and 50 T3 is quite a big dose so i doubt the amount of hormone is the issue.

I would have a read of Dr Blanchards book. It has a lot of good info in there.

Low calorie diets are terrible for the body. Your metabolism needs food to work properly. Very often the issue is hormonal and the diet, so try and address the food at least.

The Obesity Code Jason Fung is good make sure it is that book as there are a lot of books about the book with similar titles

T4 only converts into rT3 if you have a conversion problem, and therefore too much unconverted T4 in your system. If you have a conversion problem, your FT3 will be too low, and it is low T3 that causes symptoms like weight gain. But, rT3 itself does not cause weight gain.

There can be many reasons for poor conversion, but one of them is low-calorie diets. You need calories to convert. So, perhaps you have been over-doing the dieting!

But, all that is conjecture, because you haven't posted your results. Do you have copies of your results? If so, post them here, with the ranges. You could just be under-medicated - most people are.

Hi, thankyou for your reply. I think it could be the diet i was doing cambridge for 6 weeks i lost 17 pounds and gained 10 of those pounds back within 2 weeks of normal eating. Since then ive been continuing to do cambridge on and off for the last 6 weeks trying to lose the weight i gained and had zero success.

I dont think im under treated because when i last went and got it checked they said my TSH levels were 0, and i posted the results on here and everyone said they seemed normal. I suppose that could have changed i guess.

I know that rt3 doesnt cause weight gain but it slows down the metabolism even more rather than speeding it up is this correct? (just all stuff ive read online).

Does it sound like the dieting situation or something else?

Thankyou for your reply, its really appreciated. :)

I've just skimmed through your past posts, and you posted some results seven moths ago, but they were deleted, so I can't see them. And I didn't see anyone say they were normal!

In another post, three months ago, I think, SeasideSusie said that as you were taking T3, you need to have your FT3 tested. If you don't do that, then you can have absolutely no idea whether you are under-medicated or not. And, yes, a lot can change in three months! So, it's time to get your tests done again - especially FT3 - so we can see about that. Plus, it would appear that you haven't had your nutrients tested for over seven months, so they need doing again, too. It's not just about hormones. And, as you've been on and off dieting - always a bad idea! - you're likely deficient in a few things. You cannot possible get enough nutrients eating so few calories a day. Plus, the Cambridge ready-made meals contain soy flour which is an absolutely no-no for hypos (other people shouldn't be consuming it, either, but that's another story), it will make you more hypo. So, yes, I think your dieting has a lot to do with your thyroid problems and continued weight-gain.

RT3 is supposed to slow the metabolism down. That's the whole point of it. You will have high rT3 is situations where you need to conserve energy, such as serious illness, famine, etc. But that is not the same scenario as high rT3 due to high unconverted T4, due to over-medication or poor conversion. A lot of that is converted to rT3 in order not to waste the T4, because after a few hours, it is converted into T2.

However, the low metabolism it causes will only be of consequence if your weight-gain is fat. For most hypos, the weight-gain isn't fat, it is mucin, a mucusy substance found under the skin of hypos, which hold water. That is caused by low T3, and can only be removed by increasing the T3 level. But, by low-calorie dieting, you are lowering the T3 even further, thereby making yourself even more hypo. In other words, shooting yourself in the foot.

Thankyou for your reply.

I see, i had no idea my doctor would even do a FT3 test i have asked before and they declined telling me im 'normal' at which point with how i was feeling i knew i wasnt. I only go once a year to get re tested as according to my doctors they dont need to see me any sooner because im healthy, i even went to see an endo and they said i was normal and that thyroid problems have no direct link with weight gain!? which i dont believe. From what your saying it sounds like i have a conversion problem due to dieting, and ive been doing cambridge on and off for about 3 years now. (i had no idea their products had soy in i was told they were thyroid friendly!!!!) Thankyou for letting me know. At this point i have no idea what im supposed to do or eat, i considered getting a gastric band for quite some time, but if its the low cal diet causing it maybe i need to stop that completely first and see how i feel after that. I will post my results when i get them as a reply. Do you have any idea what sort of diet im supposed to be executing? And again from what ive said is it conversion or under medicated?

Just eat clean food, food that you like. Plenty of good protein and good fats - animal fats, olive oil, etc. - and plenty of fresh fruit and veg, some carbs, not to much fibre, and don't skimp on the salt.

What you need to avoid is too much sugar, all artificial sweeteners, processed oils - sunflower seed, rapeseed, etc. - and unfermented soy. And, therefore, you need to avoid processed foods, because they contain all of the above in abundance!

And drink plenty of water.

I hate the word 'diet', because it implies restriction for the sake of restriction. I don't believe in calorie-counting. You should be counting nutrients, instead. But, even so, you can be low on certain nutrients, because hypos tend to have low stomach acid. And a gastric band would make you even more deficient in nutrients. So, I would not entertain that idea, if I were you.

Do you know if you have high antibodies? If so, you might benefit from a 100% gluten-free diet, which could lower antibodies.

Doctors know nothing about thyroid. It is a universal problem. They just don't learn enough about it in med school. They rarely test the FT3 because they don't understand anything to do with T3. Therefore, you cannot ever trust them when they say that you are 'normal', 'healthy', or that any of your symptoms have nothing to do with your thyroid - because the odds are, they do. Always check up on anything they tell you. You can do that here. If you can get your levels tested privately, and let us tell you whether you are adequately dosed or not. :)

Thankyou so much for your advice and help it really does help massively a lot of this I’m still learning. I was diagnosed so young I just trusted everything the doctor told me up until a year ago and still learning now. So thanks :)!

Is there a way to test if I have low stomach acid? And what nutrients would you recommend I take vitamin D 5000iu but that’s about it at the moment? I have been allergy tested and got told I shouldn’t have gluten. I should probably exercise that.

Yeah I’ll see about getting tested. Once again thankyou for all your support and advice. It means a lot:)

You should only take what you need, but you need to get the tests done to find out.

However, you can take vit C and magnesium without testing.

For low stomach acid, see here :

Okay great, thankyou :) I have vit c and magnesium. What about zinc and selenium?

Yes, you can take a little zinc and selenium, too. But, don't start them all at once! Leave a couple of weeks between starting each one.

Okay great. I’ve learned a lot today. Thankyou! I think what I need to do is stop the Cambridge diet completely and get tested for as many as the ones you listed! Thankyou so much

I really do think you ought to stop the Cambridge diet completely, too! In fact, I think it ought to be completely banned!

Agreed. I completely feel like I’ve taken 1000 steps backwards in the direction I want to be going in. However I think stopping cambridge is gnah have a great affect and just replace it with healthier meals I guess. Also do I have to have several blood tests to receive my results or can they do it in one? I don’t want my GP to tell me no if I don’t know what they are talking about!

If you had your tests done by Blue Horizons, they could do all those tests with two tubes of blood, taken from a prick in your finger! See here :

A lot of doctors tend to be difficult about tests because of the costs - or because they're just bloody-minded!

Hi Roy, insulin resistance sets in with a high carb diet. I haven't looked up your posts but I found unfiltered apple cider vinegar very helpful. It helps to block starch, it adds enzymes and probiotics. Take a teaspoon or two diluted when you are about to eat. Get the correct type of vinegar, you may have to go to a specialty store. Consider cutting way back on starch and sugars but eat a good amount of healthy foods and excellent fats like avocado and coconut, lots of it.

Excellent thankyou for your reply and advice I’ve heard good things about apply cider vinegar. Thanks!

Could you explain more about this mucin? How can we get rid of it? Is there anything we can do to help t3?

You can only get rid of it by raising your T3 level, but it does depend how long you've had it. If you've had it for a long time, it's not that easy to get rid of, and comes back if your levels drop. Water pills might help, but they're not a long-term solution.

Not sure what you mean by 'help T3'.

Is there a way to tell if it’s mucin or just fat? Thankyou!

It's a little more complicated. High fT4 leads to extra D1 (type-1 deiodinase) which converts T4 to equal amounts of T3 and reverse T3 (rT3). Reverse T3 blocks the action of T3. So, if your fT4 is high or elevated fT3 will tend to show up as high because of D1 activity.

D2 (type-2 deiodinase) converts T4 to T3 in certan tissues. It is responsible for local control of thyroid hormone activity, which means the local activity is not well reflected in blood hormone levels. So, again it is difficult to get a good idea of conversion from blood levels.

If on diagnosis your fT3 and fT4 are low and TSH is not elevated much then I think you can deduce you may have a conversion problem as a consequence of there being insufficient TSH to stimulate D2 activity. Otherwise, it is very difficult to decide whether conversion activity is normal. Very low calorie diets do cause conversion problems since it reduces TSH and hence D2.

It would help to see blood test results, both at the time of diagnosis and now, if you have them. It may be that you are simply undermedicated.

Yes, we know it's a little more complicated than that, jim, but you're talking to a complete beginner, here. Why over-complicate things? Keep it simple.

But, while you're on the subject, would you care to explain just how rT3 blocks the action of T3?

Yeah, sorry im only 25 and got diagnosed at 17 so im still learning!

Once you are on thyroid hormone replacement - levo, T3, NDT - the TSH is irrelevant unless it goes high. A TSH of 0 means absolutely nothing. Your Frees could still be low. Dosing by the TSH is worst thing you could do for your health, yet it is something that the majority of doctors do.

As to rT3 blocking the action of T3, that is what used to be thought. It was thought that rT3 blocked receptors so that the T3 couldn't get into the cells. The latest research says that rT3 has its own receptors and does not block T3 receptors. It is thought, now, that rT3 is inert, but nobody really knows. However, unless your FT4 is high, you won't have an rT3 problem - unless it's due to the low-calorie diets, of course.

Yeah I get what you mean. Makes sense why the doctors were confused when they said my TSH was 0 as they probably didn’t understand what that meant! As I didn’t either clearly. Where should I go from here?

We would need to see results for :




TPO antibodies

Tg antibodies

vit d

vit B12



before anyone could answer that question.

And can my regular GP do these tests?

I'm afraid I can't say. You're in the US, aren't you? I don't know what available there.

No I’m uk!

Oh, sorry! In that case, then, no, your GP won't do all those tests. But, get as many as you can. Does your doctor know you are taking T3? If so, he should have the intelligence to inform the lab so that they will test FT3.

No they don’t. I didn’t tell them as I didn’t think that was a good idea? But if it gets me the tests I need I’ll tell them in the hope of getting FT3 test done. Any of the tests I can do myself? Once I’ve got the results am I too upload them to here to see what people can see?

Start a new thread with your results when you have them - so they do not get missed :-)

Yeah will do!

For full evaluation you ideally need TSH, FT4, FT3, TT4, TPO and TG antibodies, plus vitamin D, folate, ferritin and B12 tested

See if you can get full thyroid and vitamin testing from GP. Unlikely to get FT3

Private tests are available

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have money off offers.

All thyroid tests should be done as early as possible in morning and fasting and don't take Levo in the 24 hours prior to test, delay and take straight after. This gives highest TSH, lowest FT4 and most consistent results

Link about antibodies

Link about thyroid blood tests

Print this list of symptoms off, tick all that apply and take to GP

See Box 1. Towards end of article

Some possible causes of persistent symptoms in euthyroid patients on L-T4

You will see low vitamin D, folate, ferritin and B12 listed

If you have Hashimoto's then look at gluten free diet

Hashimoto's affects the gut and leads to low stomach acid and then low vitamin levels

Low vitamin levels stop Thyroid hormone working

Poor gut function can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten

According to Izabella Wentz the Thyroid Pharmacist approx 5% with Hashimoto's are coeliac, but over 80% find gluten free diet helps significantly. Either due to direct gluten intolerance (no test available) or due to leaky gut and gluten causing molecular mimicry (see Amy Myers link)

But don't be surprised that GP or endo never mention gut, gluten or low vitamins. Hashimoto's is very poorly understood

Changing to a strictly gluten free diet may help reduce symptoms, help gut heal and slowly lower TPO antibodies

This really helpful Thankyou!

Good for you, I have only been learning for about 18 months and with the help of the people on here am feeling well again. You will too, it takes time and patience, good luck.

This is interesting regarding the metabolic effect of RT3, not just that it is a byproduct, but its direct effect.

No, it's not just a by-product, we know that. But, it's still not certain what exactly it does, or even if it does anything. But, obviously, if more T4 is converted to rT3 than T3, then metabolic rate is going to fall.

Well, it is definitely an non-positive gain for T3. But it may be more than that. I think Diogenes mentioned that even though he feels that because there are RT3 receptors, therefore RT3 does not occupy T3 receptors, he said that RT3 may reduce cellular metabolism via an unknown effect.

So it may be more than just a non-positive. It could also be a negative...making it a double metabolism reducer.

What he actually said was that nobody knows what it does, if anything.

Would you suggest taking less t4?

I can't suggest that, because I don't know what your FT4 level is. All this is hypothetical because we haven't seen your full labs.

I understand I will post a new thread with my results when I get them. Thankyou:) x

You're welcome. :)

Exactly. So it is probably not good to assure people that RT3 does nothing.


Sorry about the complexity, the essential point is that it is very difficult to know if you have a conversion problem by looking at fT3, fT4 because you don't know where the T3 is coming from (D1 or D2) and the fT3, fT4 ratio varies with fT4 levels. Not saying it is impossible, just very difficult.

Complexity warning - ignore the rest if you like!

rT3 is inactive and is thought to block the action of T3 although the precise mechanism hasn't been found. D1 increases with high fT4 levels converting T4 to T3 and rT3. There are a number of possible reasons for this. By producing more inactive rT3 metabolism will be reduced. Also, increased D1 activity will mean less T4 is availiable for D2 activity - personally I'm not sure whether this will have much effect, just my guess. It is also thought that by converting more T4 to T3 and rT3 these smaller molecules are easier to reabsorb in the gut and so iodine is conserved. The truth is nobody knows the mechanism by which rT3 blocks the action of T3. It was thought it was by competitive binding to thyroid hormone receptors but I read a paper recently that dismissed this, unfortunately I can't remember the reference.

So I can't give a technical explanation of how rT3 inhibits T3 action. A good approach in these cases is to look at when rT3 is produced. rT3 is produced by D1 (T4 to T3 and rT3) and D3 (T4 to rT3, T3 to T2). D1 is upregulated by high fT4 levels and D3 by high T3 levels. Both of these are associated with overactivity and so it makes sense that rT3 has a role in reducing thyroid hormone activity.

There isn't a simple answer, rT3 is inactive, more is produced in thyrotoxic situations and in where metabolism is reduced, such as starvation diets and serious illnesses.


'It is also thought that by converting more T4 to T3 and rT3 these smaller molecules are easier to reabsorb in the gut and so iodine is conserved.'

Which smaller molecules are you referring to? Is one molecule of rT3 smaller than a molecule of T3?

'It was thought it was by competitive binding to thyroid hormone receptors but I read a paper recently that dismissed this, unfortunately I can't remember the reference.'

I read it too, which is why I asked for your version.

OK, so I get all that. But, none of that actually proves that rT3 does block the action of T3.

I’ve learned more from you today than any of my doctors have told me over the last seven years thank you

I don't suppose your doctors know that much about it! lol

T3 and rT3 are smaller than T4 and much better absorbed (thyroid hormones undergo entero-hepatic recirculation). T3 and rT3 are isomers and so are the same size.

rT3 has low affinity for thyroid hormone receptors so it will to a small extent block T3 action. Nobody knows why rT3 inhibits the action of T3.

OK, yes, I got it that nobody knows why! Or even 'if', if we're honest!

But, one more question I'd like your take on - a bit hors sujet, but still... We are always told that we need to take T4 because T3 can't pass the blood/brain barrier. But if T3 is a smaller molecule than T4, how can that be? I've never found an explanation for that. Or, perhaps, is the blood/brain barrier like a receptor, and T4-shaped, so that T3 doesn't fit in...

Ha Ha. This one always amused me. Some of the old texts always said T3 couldn't cross the blood brain barrier and there was I reading it on high L-T3 with no T4. I think therefore I am.

Clearly T3 does cross the blood brain barrier.

To the best of my knowledge T4 is taken into the brain in preference to T3 which uses D2 to locally regulate T3 levels. Transport of T3 and T4 into cells is an active process using cellular transport proteins such as MCT8, so the input of hormone into the cells is controlled. T3 does enter the brain but not as freely as T4.

Awwwwwwwww and here was me thinking I was some kind of medical wonder, because I take T3 only and am not a dribbling idiot! lol Oh well... Nice to know that my instincts were right, and the merchants of gloom are wrong, yet again!

So what you are both saying... if people are taking t3 why do we need to take t4 if t3 can freeely access the brain and blood cells without it? Does taking t3 have a positive affect?

It's not that simple. And, to be honest, no-one really knows if T4 is just a storage hormone or if it does other things, as well.

As far as the bulk of the medical community is concerned, all we need is T4, and the body will sort out the T3 from conversion. And, for the most part, they refuse to accept that some people have conversion problems - but as they mainly refuse to test the FT3, they have no idea!

So, people are always tarted on levo only, by their doctors, and if they do well on it, fine. But, if they don't, doctors tend to be totally lost with no idea what to do. That's when we have to start fighting to get T3 added to our T4. Getting NDT is even harder, because most doctors have never even heard of it!

It's usually when people finally give up on doctors, and start self-treating, that they get to try NDT and T3 only. I went from T4, T4+T3, NDT, and ended up on T3 only. But, I got very little help or understanding from any doctors! I had to find out for myself.

It's all to do with money, of course, not the welfare of the patient, no matter how much they try to pretend the contrary! And, it's all very much more complicated than that, I've just glossed over the situation, and generalised. But the up-shot is, we're all different, and should all be allowed to find what works best for us. Doctors want to stick us all in the same box with the same label. Because it's easier for them, not us. :(

Yeah I’ve been having battles with my GP for the best part of 8 years and my symptoms mainly my weight has increased regardless what I do (hence why I considered a lapband) and they did nothing to help me besides say my thyroid was working fine and ignored my symptoms time after time which is why I never go, cus like you said it seems they get stuck and have no idea what to advise!

Is NDT more useful than straight up t3 which is what I take? I take 50t3 and 100t4. Would NDT work better? (Currently on the phone making an appointment at my Gp, wish me luck!!!) I have been self medicating for a while now but the weight is still baffling hence coming to this forum and learning a lot. Yeah the range that doctors treat us all from is disgusting. How long have you only been taking t3 for? Like you said my problem is defo converting it.

What’s weird when I started taking t3 I lost loads of weight. But then for some reason gained it all back + plus more and that’s been the case regardless of the diet. It’s like no matter how much or how little t4 or t3 I take.... I never feel the difference anymore :(

No-one can tell you if NDT would be better for you. You'd just have to try it and see. Some people do much better on it, but it doesn't suit everyone. It didn't suit me, which is why I tried T3 only.

Oh okay. And if you take NDT do you only take that?

There again, no-one can predict if the T4/T3 ratio in NDT will be correct for you. Some people have to add in a little T4, others have to add in a little T3. But, the only way you will know is by trying.

Thankyou for your reply :) no i do not have those results you are referring too im afraid. If TSH levels are 0 what does this mean then? I learned that it meant your thyroid did not need anymore medication? And you say low calorie diets can cause D2 in the body but dont i want it to convert to active t3 rather than rt3 as like you said it blocks the action of the active t3 in order for my metabolism and body to work properly. I take 100t4 and 50t3 and have done for the last year or so. Since then being told my results are 'normal' and i have TSH level of 0. I havent had any blood tests recently.

Again, thankyou for your reply!

Are you self-treating with T3 or has a doctor prescribed it? Don't accept 'normal' as your results. Get the numbers!

Yeah I self medicate. I stopped listening what the doctors said after my last results and also after the endo told me my thyroid was working like a normal persons thyroid would!! I go by how I feel I guess but I don’t think taking more is necessarily the right thing today which is what I’ve learned in this case

I self-medicate as well. I am currently taking 2 grains of NDT and about 25 mcg of additional T3. So in all I get 76 mcg of T4 and 25 + the 18 in NDT. So between 40 and 50 mcg of T3. I used to take 150 mcg of T4 and a bunch of different synthetic combinations of T4/T3. I definitely feel better with less T4 in the mix.

That’s really handy to know. Thankyou!

T4 converts to T3 and RT3 in everyone. It is not only if you have a conversion problem. The ratio is what changes.

Well, yes, of course. Did anybody say the contrary?

You did. Earlier in this post.

'T4 only converts into rT3 if you have a conversion problem, and therefore too much unconverted T4 in your system.'

Sorry, I missed a word. I should have said 'T4 only converts to excessive rT3...' Thanks for picking up on that. :)

Okay, just making sure we're all on the same page.

Oh okay, so it’s more the fact that it doesn’t convert enough of it? So to dumb it down t4 - rt3 - t3 - t2 is how it should be?

T4 converts at a pretty steady rate. It converts to T3 and RT3 at a normal ratio of approx 60/40. Under stress, dieting, etc a larger proportion of T4 converts to RT3 and a smaller portion to T3. Both T3 and RT3 become T2.

RT3 is not an active hormone. So at the very least it is wasted T4. However, some feel that it impedes cellular ability to use the active hormone T3 as well. If that is true, you can see why you would want to have more T3 and less RT3.

No, it's not wasted T4, that's the whole point. Excess unconverted T4 is converted to rT3 so that the T4 isn't wasted, because the rT3 is converted to T2.

Royheravi, rT3 cannot 'convert' to T3. Nor can T3 'convert' to rT3. It's one or the other.

It is wasted from a metabolic standpoint. Correct, it is not wasted from an iodine standpoint.

But I think energy/metabolism is what we are shooting for here...

Energy/metabolism is what I’m referring too. But I suppose it’s useful to know how it works both ways! Thankyou!

Okay so the goal is for the t4 to convert straight to t3 then? But what I don’t understand... if I’m taking t4 and t3 maybe I don’t have a conversion probably but my diet is messing it up? Is this possible?

Dieting will reduce the amount of T3 and increase the amount of RT3 that is converted from T4. You cannot have 100% conversion of T4 to T3. RT3 acts as a buffer and is normal in some amount. Reducing the amount of T4 you take is a way to decrease the total amount of RT3. You just need to take enough T3 to make sure you have enough FT3 in your blood.

Does it reduce it even if I take extra t3? This is what I don’t understand what happens to the t3 that I take?

The T3 you take needs no conversion. It directly contributes to your FT3 serum level. So, you want the FT3 level to be in the upper part of the range. Some of it comes from the T4 you convert, and some of it comes from the T3 you take.

I just read some of your previous posts. You are taking birth control pills? The estrogen in those pills increase binding proteins, therefore reducing free hormone levels. Have you had thyroid labs since starting the pill?

In any event, if it were me...I would reduce the amount of T4 to 75 for starters. 50 mcg is a pretty good amount of T3, so I would leave that alone for now. It may actually be more than you need in the end. See how you feel.

Yeah I was but I’m currently having a break from birth control pills! And when I did have my thyroid tested while taking the pill again the doctors said I was “within normal range” yeah that’s what I’m thinking about doing! I’m booked in to have tests some time next week so fingers crossed. Thankyou for your reply and help :)

I would love more info on taking birth control and its effects on ndt. I have been taking NDT and was ok for while. All of a sudden the last couple of weeks I am so tried. And so hungry all the time. Usually I crave seeets. For the last few month I have been better. Not the last month I crave sweets all the time. Feel hungry all the time and have zero energy even though I have been taking my NDT. I really thoightof stopping birth control but don't want to get pregnant. I know in a few years I may go into menopause but worried to take any chances right now. I looked into a coil Implant butthst was horrible. Even worse horror stories of the women have have done so. All ending woth having to remove uterus and tubes to get better and not completely with thst. So I gave up that idea quickly

I don't know a lot about it, but I read that increased estrogen (ie birth control) increases binding proteins. I read that it may cause an increased need for thyroid hormones. Do you have your thyroid still?

You have to remember, it's not just about converting T4 to T3. Some of your T3 has to be converted to T2, and some of your T2 has to be converted to T1. It's all conversion, and needs energy (calories) to work.

Nobody really knows what T2 and T1 do, but they must be important, or the body wouldn't make them, would it. :)

Right, thankyou for clarifying that for me. All new information! Taking some understand so I appreciate you taking the time to reply :)

When we take levothyroxine (T4) it can cause weight gain and is the commonest query on the forum, i.e. weight gain. It can be due to too low a dose or not converting it into sufficient T3. T4 is inactive and has to convert to T3.

In the past I’ve taken higher doses of levothyroxine I certainly didn’t loose weight. I did get palpations and a resting heart beat of 104.

I eat healthily although I do have the odd surgery treat cannot loose weight unless I constantly do severe exercising 4/5 times a week which after working full time and being a single parent is totally exhausting

Severe exercising depletes T3 in our body if we aren't on an optimum of thyroid hormones. Even if we are on an optimum, exercise should be gentle. T3 is the only Active Thyroid Hormone required in our body as it drives our whole metabolism. Brain and heart have the most T3 receptor cells. Therefore, if we don't have sufficient T3 to run our whole metabolism, we do not feel well and also have disabling symptoms.

Oh wow. If my t3 levels are perfect for my body can I then do Normal - high intensity exercise or even then no?

We have to 'listen' to our body from now on as the 'energy' is 'artificial if you like' due to taking replacement hormones.

You can exercise to 'tolerance' and I think you will gradually learn what is optimum for you in that afterwards you should not feel unwell or have clinical symptoms returning.

(I am not medically qualified and had undiagnosed hypothyroidism).

It is wrong that your doctor won't test T3 when you are taking it! It should read high in the range if you are correctly dosed but on no account should it be over range as that isn't good for you. If found to be slightly over range then the word is you may have a virus that you aren't aware of but that is pushing it up so rest in a few weeks to check it has dropped back over wise drop the dose a little.

Thankyou for your reply. Yeah I’ll get them to test for t3 and post my results on here instead of taking their word for it!! What kind of virus would be affecting the weight gain?

A virus can push up your FT3 reading not your weight.

Not quite "on no account should it be over range as that isn't good for you", because some of us here have peripheral resistance to thyroid hormone and need very high doses of liothyronine! However, I only wanted to mention this problem without going into detail, as Royheravi has enough to read up on for the time being. :-)

Just sharing my experience. I was on 100-150mcg T4 daily (fluctuating with seasons) and decided I didn’t want to rely on medicine because I don’t find it ideal for me (I became allergic to wheat and soy after starting it and didn’t feel it was doing my heart health any favours). I trust that I can heal my body with a healthy lifestyle and diet and slowly lowered my dose. I’ve now been on 50mcg every third day (2 days no T4 inbetween, apparently a break helps with conversion) for 3 months and to my surprise I did drop weight especially around my belly and arms and I eat considerably less without effort. I actually expected to gain weight. Also, I’m significantly more energetic and feel like a normal person at last! I haven’t done in almost 2 decades! My thyroid used to hurt when I became emotional but it hasn’t done since I’ve lowered my dose. I can’t wait to see what another year of living a healthy lifestyle will do. Hopefully the allergies completely disappear, it’s improving :-)

Never give up!! It’s all trial and error to find what works.

This is really interesting, I’m considering lowering my t4 but heard it’s extremely dangerous?! Are you continuing to stil lose weight? That’s really good to hear you feel normal! Did the doctors recommend dropping or was that your decisions?

Thankyou for your reply :)

Doctors always said the same to me that it’s extremely dangerous to lower dose on my own because I could fall into a coma. In the past when winter came my blood pressure would drop extremely low and so would my heart rate (30 something) and I needed to increase dose to boost it every winter. I go to my regular check ups every 12-24 weeks, and the doctor basically just looks at my TSH and suggests a dose according to that and then I tell them how I’m feeling and we compromise on a dose. It really is up to me at the end of the day and I adjust it according to how I feel even inbetween check ups. My blood pressure and heart rate is a great way to check I’m doing ok before any symptoms show and I check this daily.

I didn’t tell the doc my plan to eventually come off T4 because for professional reasons they would never be able to agree anyway. So I have been lowering my dose without them knowing and I look forward to my appointments to see how it affects my TSH. In April the doc increased my dose to 150mcg and I got incredibly ill after 8 weeks on 150mcg. So I started lowering myself before my appointment in August. In August my TSH was fine on my lowering dose, but I knew this test meant nothing because it takes a while for dose change to affect TSH levels. My next appointment is next week. Now that it is winter, usually I would take more T4, but I’ve stuck to 50mcg every 3rd day since September and feel this is the real test now (blood test and test of surviving winter). I did have a few days when I felt more tired, but that passed quickly (maybe normal people need a few days to adjust to weather change too?). I’m not feeling cold like I used to (toes would turn blue then white!) and my blood pressure and heart rate are great (they did dip for those few days I was tired). No matter what the doc says next week, I’ll continue to adjust according to how I’m feeling. TSH is affected by exercise and other factors so it’s not a great way to adjust our meds anyway.

Regarding weight loss, as part of my healthy lifestyle I’ve adopted regular exercise but I ate mountains of food on a higher dose and my belly could not keep weight off. In April-June weight came off on the too high dose but by July I was so debilitated (heart rate was alarmingly high and blood pressure was much higher) I mostly stayed in bed debilitated for a month and the weight piled back on. In Aug I started pushing myself to move very gradually and started lowering my dose faster. By September I got to my current dose and had no bad side effects. By late November I felt incredible and have gradually built my fitness (heart muscle which was strained by the too high dose) back up. The weight on my belly and arms dropped off very quickly in September like it wasn’t actually fat but bloating, swelling or mucin and has stayed off. I wasn’t fit in September, so it wasn’t from exercise and it was really very quick. I have never seen this waist that I have now. I do weights at the gym so my weight is not lowering but my waist is still getting smaller and I’m seeing abdominal muscles starting to show. I’m basically not puffy anymore and am being rewarded for my time doing exercise, where it was immensely difficult to see any asthetic rewards before. Last year when I begun this healthy lifestyle, I spent all my time and energy in the gym and hiking and I did get into shape but it wouldn’t stay. My abdominal muscles would peek through for half a day at the most and be gone. Now I’m exercising much less and getting rewards!

Happy to share my experience, because I know how life changing it is to be well again! When I read the emails from this forum I feel sad that so many people are going through the hell of thyroid issues and probably not enough people who are feeling better are sharing what worked for them, because well people are busy living well!

From what I have experienced and what an endocrinologist specialist told me is that t3 can help with a Little bit weight loss verses only taking synthroid or levothyroxine which is all t4 and your body converts some into t3,

This has been my experience with Nature Throid. I am on 195 per day (3grains, I believe)

I was diagnosed as hypothyroid 2 years ago, aged 60. I have struggled with my weight all my life. I know every diet and been a member of several dieting clubs and, for me, the weight loss was only temporary. I watched a documentary about the Glycemic Index and learned how the body responds to certain foods. It has changed my life. I stopped eating /drinking anything with sugar in it, including alcohol. I cut out anything processed. I swapped white rice and pasta for their wholemeal versions.....etc There is a lot of information available online and lots of books. I ate 1400 calories a day and didn't feel hungry as I was eating healthily. I lost 40 pounds very slowly in 14 months to reach a healthy weight. Now I have the occasional glass of wine, dessert, chocolate bar, but I know that if I go back to unhealthy food I will put weight back on. It's a way of eating for life. I was a size 18 now a size 12 and been at my goal weight for 15 months. You can do it!

Thankyou foryour reply. That’s good news, I think a lot of my problems have been my dieting tbh. I’m gnah get tested in the new year and start a fresh diet and know where I stand with my vitamins and minerals as well as thyroid function! I hope you continue to loose weight!!

Just want to chime in about water intake. Your weight (as suggested before) could be because of water retention. My medical history is extensive but suffice to say, I take frusemide/lasix and/or other diuretics because of heart issues and no thyroid. I went from 105kg down to 90kg in one single night (hospital, drip - frusemide), then over the week, down to 75kg. All of it was water.

Also, the more water you 'take in' the harder the heart has to work, which in turn increases water retention. Its a slippery slope if ever there was one.

Ask your doctor about water retention and/or diuretics.

Note: Hypothyroidism is linked to slow heart rate.


Wow that’s really interesting. Was it a tablet? And do you still take this? I know I retain water A LOT but too an extent I thought that was normal. What would you recommend solving this? That’s really good you’ve finally cracked it! Thankyou for your reply

I take 80mg (2 x 40mg tablets) of Lasix (Generic name is furosemide) per day. It's usually for Edema, but its prescribed whenever there is fluid retention caused by any condition.

Be warned that some people are very sensitive to it and others are resistant. Also, too much can cause kidney damage (renal failure), which is probably why doctors need a good excuse to use it, and/or monitor kidney function through ongoing blood tests.

Lots more info here:


Probably should check with doctor about your water retention, it was the first sign of heart issues for me.


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