Last August, my endocrinologist agreed to prescribe me T3 (Thybon) I started taking it, and in the same cycle, I got pregnant. Unfortunately, I miscarried at close to 12 weeks, and I feel that T3 may have been the reason I got pregnant—but also the reason I lost it.
I started taking 88 mcg of Euthyrox and 12.5 mcg of Thybon. About four weeks later, when I got a positive pregnancy test, my doctor increased to 132 mcg Euthyrox and 25 mcg Thybon.
I’m trying to understand my thyroid levels and would love your insights. Below are my test results:
Thyroid Panels
July 2024 (Pre-T3 treatment - on 75mcg Eutirox)
TSH: 1.92 mIU/mL (0.27–4.2) > 42%
FT3: 3.82 pmol/L (3.1–6.8) = 2.48 ng/L > 19.5%
FT4: 14.04 pmol/L (10.0–24.5) = 10.9 ng/L > 27.9%
September 2024 (around conception, on 12.5 mcg Thybon/88mcg Eutirox)
TSH: 2.0 mIU/L (0.400–4.2) > 42.1%
FT3: 2.3 ng/dL (2.1–4.4) > 74.8%
FT4: 1.5 ng/dL (0.70–1.8) > 72.7%
October 2024 (4 weeks + 4 days pregnant, still on 12.5 mcg Thybon/88mcg Eutirox)
TSH: 0.866 mIU/L (0.100–2.5) > 31.9%
October 2024 (2 days later, either still on 12.5 mcg or already increased to 25 mcg/132mcg Eutirox—unsure)
TSH: 0.785 mIU/L (0.100–2.5) > 28.5%
November 2024 (Day of miscarriage, 11 weeks + 4 days pregnant, on 25 mcg Thybon/132mcg Eutirox)
TSH: 0.008 mIU/L (0.100–2.5) > -3.8%
T3: 234 ng/dL (81–190) > 140.4% (Tested T3 not FT3)
FT4: 2.0 ng/dL (0.700–2.0) > 100%
February 2025 (3 months post-miscarriage, back to 12.5 mcg Thybon/88mcg Eutirox)
TSH: 0.028 mIU/L (0.400–4.2) > -9.8%
FT3: 3.3 ng/dL (2.1–4.4) > 52.2%
FT4: 1.4 ng/dL (0.70–1.8) > 63.6%
My Questions:
Was I overmedicated when I got pregnant (from 12.5 mcg to 25 mcg Thybon after the positive test)?
Is it safe to take T3 during pregnancy? One endocrinologist told me T3 is prohibited, but I’ve heard conflicting opinions. My endocrinologist says I should take it, but I also don´t trust that he has experience working with T3.
Is the suppressed TSH normal while on T3? What are the new reference TSH values when taking T3? I’ve read that this is common and not necessarily a cause for concern—what is your experience? Will I ever have a "normal" TSH while taking Thybon?
Even though I returned to my initial dosage a few months ago, my TSH hasn’t changed much. Is this normal?
Every time I leave an endocrinology appointment, I feel so confused and disheartened. What should I do, and who should I trust when opinions on this are so contradictory?
Looking forward to your feedback!
Really appreciate your time on this.
Gratefully,
PS: I have been addressing all other vitamins and minerals. Blood tests were done fasting, before 9 AM, and at least 24 hours after my last dose.
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xtrelinhax
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First of all, TSH is the least important number. The most important number on blood tests is the FT3, followed by the FT4. TSH doesn't do much, apart from instruct the thyroid to make more or less thyroid hormone. It's just a chemical messenger from the pituitary to the thyroid. So, we tend to ignore it on here, unless it is high or does not correspond to thyroid hormone levels.
Was I overmedicated when I got pregnant (from 12.5 mcg to 25 mcg Thybon after the positive test)?
In September 24 you were not over-medicated, no. Levels were good, around where one wants them to be.
Is it safe to take T3 during pregnancy? One endocrinologist told me T3 is prohibited, but I’ve heard conflicting opinions. My endocrinologist says I should take it, but I also don´t trust that he has experience working with T3.
Millions of women give birth every day with good levels of T3 coursing through their veins, made by their thyroids. Why would it be unsafe to take it when you're hypo? It's exactly the same hormone as is made by your thyroid. Euthyroid women do not stop making T3 when they're pregnant so one has to assume that it's safe.
But most doctors are terrifiend of T3. They do not understand what it is or what it does - their education in hormones is very limited - and they don't want to prescribe it. Obviously if you're pregnant you don't want to take too much, but neither do you want to take too much when you're not pregnant. But T3 is the active thyroid hormone needed by every single cell in your body to function correctly.
It's mainly T4 that crosses the blood placenta barrier to support the baby, so you do need good levels of that. But T3 can cross it. I have heard of women having successful pregnancies on T3 only. And, we also have to think about you're health because you're the one doing all the hard work. And you need T3. I certainly don't think it's prohibited.
Your endocrinologist made a lot of mistakes. Whether that's down to lack of experience or lack of knowledge I don't know. But he had no justification for putting you on T3 in the first place. You were under-replaced but the logical thing to do was increase levo first before putting you on too high a dose of T3 - one normally starts on 5/6.25 mcg T3, not 12.5. And doubling the dose just after conceiving could have been too much for your body to handle. Increases shouldn't be more that 6.25 mcg at a time. But whether that would cause a miscarriage is impossible to say.
A suppressed TSH is perfectly normal when taking T3. And it really doesn't matter. It is suppressed because your pituitary esteems that you do not need it anymore. And you don't. It's only a very rough guide to thyroid status, anyway, and not 100% reliable.
And yes it's normal for the TSH to lag behind. It's process is more complicated than just swallowing a pill. But it doesn't matter. Ignore the TSH.
Now you're back on levo only, if I were you I'd seek an increase in that until my FT4 got up to about 75% through the range. Then have a good look at your conversion rate - or post the numbers on here - to see if you really need T3. Obviously taking it when you did made you feel better, because your FT3 was low. But so was your FT4. You were very under-replaced. Get your FT4 higher in-range and you may find your FT3 increases with it. If it doesn't, then it will be obvious that you do need the added T3.
I have no idea where you can find a doctor with decent experience. And it's not just lack of experience you're dealing with, it's also prejudice against T3, which a lot of doctors have. And I think quite a few deliberately set you up to fail so that they will then be able to say: see? It was lack of T3 causing the problems to begin with! And take you off it for good.
You need what you need. And if you need T3 then nothing else will do. But if you don't need it, why put yourself through all this trauma to get it?
Thank you! I’m actually still on 12.5 mcg Thybon + 88 mcg Euthyrox, I never stopped the T3.
You are right! I did start feeling better with the T3. And I tried to stop it after the MC but symptom returned.
I’m about to start a fertility treatment, so I’m unsure what the best approach is. Would you recommend stopping Thybon and increasing Euthyrox instead? Or should I maintain 88 mcg Euthyrox and retest before making any changes?
Also, how long would it typically take to see an improvement in my numbers after adjusting my dose?
Well, yes, they would, because if you stop T3 you need to increase levo to take up the slack. And that takes time. And it's low FT3 that causes symptoms.
I think it would be best to get full thyroid testing before making any more changes. Too many changes in too short a time is not good. And it's only been about six months and a lot of changes. So best to leave things as they are until you know what's what and where you stand.
But these things don't go by time-lines, they are totally unpredictable. And it's not just about the numbers, it's more importantly about how you feel.
I actually just did a full thyroid panel last week—my February 2025 results are the most recent. I was in the same dosage since December. I feel like now is the time to make the best possible adjustments to prepare for treatment.
Given these results, in your opinion, should I stop taking Thybon and increase Euthyrox?
I see no reason why you should stop the T3. If you are trying to get pregnant just leave things alone. Once you get pregnant then you will need to increase the levo, but for the time being, if it were me, I'd just leave things as they are.
I do feel more stable right now, even though not 100%. But in the absence of certainty about the next steps, I’ll leave things as they are. You’re right also that there have been a lot of changes in the past six months, though they were spaced out by about 2months.
I have an appointment next week with a doctor in the UK who, so far, is the only one I’ve heard of with experience in T3. Hopefully, that will give me the reassurance I need.
Thank you so, so much for your time and feedback, I deeply appreciate it!
FT3: 2.3 ( 2.1 - 4.4) would be 8.70% , not 74.8% ..... could you clarify ?
well , it was quite a large increase of 44mcg levo and 12.5mcg T3 dose . i think pregnancy guidelines usually advise an increase of 25mcg levo after conception. So certainly seems a bit heavy handed.
and it sent fT4 to 100%, and total t3 significantly over range ...but it's not easy to gauge what fT3 was from that... but likely to be quite high i would think.
and for testing bloods when taking T3 , 24 hrs is too long ... it's usually recommended that tests should be 24hrs from levo and 8-12 hrs from last dose T3 (move T3 dose the day before to get 8-12 hrs gap) ... other wise you don't get a true idea of average ft3 levels for much of the day. ......so if you left 24hrs from last dose levo and T3 , then all your results are showing fT3 a bit lower than it really is for much of the day.
so the dose increase was more than was needed, but it's just not possible to know if this is related to miscarriage or not , i'm afraid you'll never have an answer to that.
You’re absolutely right—I just double-checked, and FT3: 2.3 (2.1 - 4.4) is 8.70%, not 74.8%. I appreciate the correction.
At this point, I just want to figure out the best way forward. Given my latest results and upcoming fertility treatment, what would you suggest? Should I adjust my medication or stay the course for now?
TSH: 1.92 (0.27–4.2) > 42% ... these results show a levo increase was needed as Greygoose suggested, ie no obvious need to add T3 at this stage .,if you had just increased levo to 100mcg... you would expect fT4 to rise, and hopefully fT3 to go up too.
FT3: 3.82 pmol/L (3.1–6.8) = 2.48 ng/L > 19.5%
FT4: 14.04 pmol/L (10.0–24.5) = 10.9 ng/L > 27.9%
September 2024 (around conception, on 12.5 mcg Thybon/88mcg Eutirox)
TSH: 2.0 (0.400–4.2) > 42.1%
FT3: 2.3 ng/dL (2.1–4.4) 8.7 % seems ....odd that fT3 fell lower after increasing levo and adding T3 ... i'm not sure what to make of that .
FT4: 1.5 ng/dL (0.70–1.8) > 72.7% ....
February 2025 (3 months post-miscarriage, back to 12.5 mcg Thybon/88mcg Eutirox)
TSH: 0.028 mIU/L (0.400–4.2) > -9.8%
FT3: 3.3 ng/dL (2.1–4.4) > 52.2%
FT4: 1.4 ng/dL (0.70–1.8) > 63.6%
current results on 88/12.5 look good on paper, so no obvious reason not to carry on and j consider a small 25mcg levo increase if needed when you conceive again ......
but ;
a) you don't know what effect simply increasing levo would have had (without adding any t3) ..... you might do just as well on levo only at an adequate dose .
b) taking T3 during pregnancy is going to mean you butt heads with every medic / midwife you meet , which given your recent loss , is going to be very stressful / unsupported for you .
personally , i'd try to go the route of less stress .. ie go back to levo only , take a few months to get dose optimal / stable first before even trying to conceive and save any adventures with T3 until afterwards, when it's just your own body your dealing with ,
ok ,, if it turns out that you simply can't get pregnant without taking T3 then so be it, 'pregnant and taking T3' might be a route you have to travel ...but it's a tough gig ,,,, you'll be told at every visit/ everywhere that your putting the baby at risk... which even if it's not true, will be very difficult for you .
.......in my opinion, it's not true that (appropriately dosed and monitored) T3 is risky for pregnancy ~ it simply can't be ~ hypothyroid women had babies successfully for decades using NDT before levo was invented (NDT= T4 + T3 from pig thyroid gland ),, and pigs have significantly higher T3 :T4 ratio's than humans do ...ie those women would be having significantly more T3 than 'normal/ healthy ' mothers had from their own thyroid gland.
I went back to check my papers, and I believe that on the day I did those blood tests in September, I hadn’t started Thybon yet. That would explain why my FT3 was low. Blood tests were done on 20 Sep and started Thybon the day after.
I see your point that I should have tried increasing levo first before adding T3. I´m feeling ok on 88 mcg levo + 12.5 mcg T3 now but not 100%.
My main concern now is how to navigate treatment when (or if) I get pregnant again. While I feel better now, I don’t know whether I’ll be able to conceive or what adjustments will be needed to support a healthy pregnancy. I also want to ensure that my thyroid levels are optimized to increase my chances of success with IVF.
I really appreciate your reassurance that T3 isn't inherently risky for pregnancy—it’s helpful to hear about past evidence from NDT use. That said, I completely agree that T3 during pregnancy will be an uphill battle, dealing with doctors who don’t understand or support it. That’s why I’m looking for a doctor, or someone, who has real experience with T3 and pregnancy, so I can move forward with confidence.
I’ve heard of a professor in the UK who apparently has experience with T3, and I have an appointment next week to get his opinion. Hopefully, that will help me make a more informed decision.
As for waiting to stabilize before trying to conceive, I completely understand that logic, and in an ideal world, I would do that. The challenge is that I don’t have time to lose. I’ll be 40 this year, which is the age limit for fertility treatments in the public hospital.
That said, after my previous experience, I also agree that I would feel safer adjusting T3 when it’s just my own body at stake. But at the same time, I truly believe that T3 allowed me to conceive in the first place, which makes me hesitant to drop it completely. That’s why finding the right medical guidance now is so important to me.
Thanks again for your thoughts, I really appreciate the discussion.
I have found that a raise in dose of either T4 or T3 will increase Free T4 and/or Free T3, and reduce TSH. If I then continue for 8 - 12 weeks without changing dose my Free T4 and Free T3 will reduce and my TSH will rise. It can take a long time for my results to completely settle down after I change something.
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Note : Ferritin is a measure of your iron stores.
Back in my 30s I did IVF 5 times and got pregnant 3 times. I lost them all in the first trimester.
I had been told that my thyroid was "underactive" but not enough to need treatment. I'm sure that had something to do with the losses I had. But I also suspect that I was low in iron and ferritin and possibly some other nutrients as well. This all happened in the days before the internet so I knew nothing.
I would urge you to not only try and optimise your thyroid hormones before conceiving again, but also try to optimise your iron/ferritin, vitamin D, Vitamin B12 and folate. Ask us for advice on the form of supplements you should take if it turns out yours are low in range or under range - supplements vary a lot in how good they are and what the active ingredients are made of.
Doctors are quite happy to tell someone with a ferritin level of 20 with a range of 13 - 150 that their iron levels are fine. But as a patient you might feel best with a level of 100. Doctors dismiss this kind of thinking because they think any result in range - anywhere in range - is "fine", but if you want a healthy baby you need to be as healthy as possible yourself.
Thank you for sharing your experience and the link! It’s so helpful to have a space to discuss this.
I’m also really sorry to hear about your losses. That must have been incredibly difficult.
I’ve been closely monitoring my vitamins and minerals, and they’ve been within range, but it’s taken a LOT of work and supplementation to keep them there. I’d love to hear your supplement suggestions, especially since I struggle with iron, magnesium, and vitamin D absorption.
When I conceived and throughout the 12 weeks of pregnancy, my levels were okay, but they’ve actually dropped quite a bit now. I think part of it is because I’ve lost some of the drive and motivation to stay on top of everything as strictly.
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