T3 only pregnancy

Good evening all

I presently take T3 only... long story, was confirmed as being allergic to T4 (levothyorxine) so instead prescribed T3 (liothyronine) only treatment and life has improved since, all the nasty side effects which I experienced on T4 went within around 4 weeks of coming off the medication.

I'm now of an age where I'm thinking about a having a child, however, if being on pure T3 medication meant any risks then I would not pursue it. I've seen two endo's, the first (who wouldn't prescribe me T3 at all) was dead against the idea of a T3 only pregnancy (apparently there hasn't been a single test/study/research of a T3 only pregnancy), he went onto list all the associated risks such as cretinism etc... he put a lot of fear into me so I resigned myself to the fact I would probably be childless.

However, Endo No.2 (who prescribed T3) seemed relaxed about the idea... I'm mixed. There's no way I can tolerate any T4.

I'd love to hear from any mum's who experienced a T3 only pregnancy.

Thank you



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17 Replies

  • Kate,

    I don't think there will be many women who take T3 only during their pregnancy as most endos will try to persuade them onto Levothyroxine which is obviously not an option for you.

    Why not Google "T3 only pregnancy".

  • Risk of cretinism? Where on earth would he get that idea from? Cretinism is caused by lack of a thyroid going undetected and untreated. The first thing that all babies have is a blood test for thyroid and phenylketonuria, amongst other things, immediately after birth. He was a shameless scaremonger. In order to utilise the Levothyroxine, it has to be CONVERTED into T3! There are far more likely to be problems if you were to go back onto Levo and it made you ill.

    It is probably comparatively rare to see a T3only pregnancy, but there is really no reason why it should not be just the same as taking Levo, or indeed having a normal thyroid, so long as you did not overdose and end up with raised blood pressure (which, of course, also applies to Levo.)

  • Cretinism? What a load of rubbish? T3 is the active hormone, so that is the one your baby needs. If you aren't spreading your dosing through the day it might be a good idea to do so while pregnant, since the half life is so short.

    There may not be much in the way of studies on T3 only preganancies, but I bet there are some for NDT. Have you considered trying that?

  • You should read this :


    I have never researched this myself because it has never been relevant to me, so can't offer any other links.

    As someone on T3-only I can understand why you might be reluctant to give it up for 9 months or more.

    There have been posts on this forum from women who have had very successful pregnancies on NDT. I think they might be quite hard to find though, since the search function is so dreadful.

  • Hi, I was on T3 only before I was pregnant, so my gp told me that I need to be on T4 medication only when I will be, so now I am 8 weeks pregnant taking 50 mcg of levo only and retesting every 4 weeks until my levels will be ok. I feel awful lot of nauseas and soooo tired, but I will wait until the first trimestrer and then maybe I will introduce some T3 with my T4 depend on my levels and symptoms... My B12 is low too I would like to supplement it to but I dont know if I can during pregnancy, I will ask my doctor if I can or not.

  • Low B12 is definitely not a good thing to have during pregnancy. You should supplement. See this link :


  • You definitely should supplement B12 in pregnancy. And methyl folate too. Baby risks birth defects without adequate methylation.

  • I am taking methylfolate but my b12 is 330 I would like it a little higher, i have at home b12 methylcobalamin from solgar 1000mcg but I dont know if is harmful or not for the baby. I did not have yet any scan until my 12 week so I am pretty scared... Too many things suddendly plus the thyroid game too...aaahh and high antibodies to add to the mix... :(

  • Go on a gluten free diet which can help antibodies.

    Ideally, your B12 level should be 800-1000, or even higher.

    For more info on supplements Google:

    Ben Lynch Prenatal Supplementation Optimizing your Future Child.

    In a nutshell, Solgar B12 is a good start, but may not be sufficient.

    Good luck!

  • Thanks! I am gluten free since two years ago, and my tpo dropped from 1500 to 1000 but I dont know how they are now..

    Ok I will investigate about the b12 and I will start to supplement.

    Thanks again!

  • Hello, I'm on t4 and t3, 24 weeks pregnant. T4 only makes me very ill. I know of ladies who have had successful t3 pregnancies only too when they didn't using t4. Conventional medicine seems to demonise t3 since t4 was introduced...without any trials, is my understanding. Before that women took NDT and I anticipate millions of babies would have been born from the early 1900's to 1950's before levothyroxine was invented. T3 is what keeps us alive, t4 is inactive and needs to be converted to t3 to have any health benefits for us. There is a great pregnancy support group on Facebook called Thyroid Disease and Pregnancy. Hope this helps.👍

  • Hi everyone

    Thank you all so much for your prompt replies - greatly appreciated :)

    Yes, interestingly, reading the comments I can see my thinking is inline with others, e.g. as T4 needs to be converted into T3 to be used my mother and baby then why would readily converted pure T3 be harmful? Apparently babies categorically need T4 - but why? I will research this specifically.

    Thanks for the links to research - I will read. I have googled 'T3 only pregnancy' but I've found absolutely nothing... think I might even contact a T3 manufacturer directly so see if they have funded any research in this area.

    Interestingly, as a few of you suggest, I've found information re successful NDT pregnancies but sadly my endo has totally ruled that out... he would only entertain it if the T3 hadn't worked and even then he was greatly reluctant; his argument being that the quantities in every batch of NDT vary greatly and are unreliable and therefore 'dangerous'.

    However, he did say I could have a 100% T3 pregnancy and at the time I didn't dig in to his thinking too much because I wasn't sure I wanted a baby but now I am going to schedule another appointment to discuss in detail.

    To the Mum's to be on this thread - best of luck, I wish you happy pregnancies :) xx

  • Hi KateUK, just wanted to say I've been researching taking t3 only during pregnancy. I haven't been able to find much but I did find this abstract: endocrine-abstracts.org/ea/...

    Please let us know what you uncover! I'm 18 weeks pregnant and taking liothyronine only. TSH is normal but free t4 is below normal. I'm coming across lots of info on the web about having adequate free t4 for normal fetal brain development. With my reading being 0.39 I'm concerned to say the least!

  • Hi KateUK,

    Are you a member of the "Recovering with T3" facebook group? I think some of the group members have had their babies whilst taking T3-only....It may be worth asking them.

    Take care


  • Kitten, i didn't even know there was a Facebook group - i'll check it out. Thanks very much x

  • Hi KateUK,

    How has your pregnancy been on T3 only? I am in a similar situation, although not pregnant yet, but will try soon and am worried about being on T3 only.



  • Hi KateUK,

    How has your pregnancy been on T3 only? I am in a similar situation, although not pregnant yet, but will try soon and am worried about being on T3 only.



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