Pregnancy, T4 & T3

[thyroid-warrior]

Hi, I just tested pregnant today.

Currently, I'm on 100mg T4 and 20 mg T3 since 17 February (24 days).

Felt better on this dosage since 1 March and energy and periods of anxiety have decreased.

Haven't tested my TSH, FT4 and FT3 since January.

I have called my GP to inform them about the pregnancy and to enquire about the next steps.

My original plan was to go for (full private) blood test at the end of March but due to the pregnancy, I've decided to book in for the GP thyroid function test for Friday.

What I understand they most likely won't test for FT3, usually would just be Ft4 and TSH.

What I've heard is :

uhsussex.nhs.uk/resources/p...

What happens before pregnancy?

Ideally, your thyroid blood tests should be checked before you start trying for a baby, so that your thyroxine dose can be adjusted if necessary. Your GP can arrange this for you. Rarely, some patients with hypothyroidism are treated with a combination therapy of thyroxine (T4) and triiodothyronine (T3). T3 does not cross the placenta, so treatment should be converted to thyroxine alone before pregnancy or as soon as possible after a pregnancy is confirmed.

What happens once a pregnancy is confirmed?

As soon as a pregnancy is confirmed with a positive pregnancy test, your thyroid blood tests should be checked by your GP. Often the dose of thyroxine needs increasing early in pregnancy, for example by 25 microgrammes per day. You should not delay getting your thyroid blood tests checked. After these immediate tests and dose adjustments, your GP may refer you to the antenatal clinic at the hospital for further monitoring and dose adjustments during your pregnancy.

The GP is trying to get me an appointment with the specialist (can't remember the exact name) with my condition. I'm also considered high risk as I'm also over 40 and this is the first. I had a miscarriage at the end of the 5th week back in August.

My question is, is it recommended to increase my T4 dosage straightaway or would it be useful to wait till the blood test results come back?

And what if the specialist ask me to stop my T3? Thank you in advance!

[greygoose]

Ah but T3 does cross the blood placenta barrier. That is old thinking. So, no reason why you should stop your T3. You may need to increase your levo, depends on the level when tested - probably, actually, because taking T3 tends to reduce the FT4 level. But your blood test will tell you that. But, there's no reason why you shouldn't take T3 as well. The T3 is making you fit and capable of coping with the hard work of pregnancy and childbirth. We have to think about the mother's health as well as the baby's.

[thyroid-warrior in reply to greygoose]

100% agree with "We have to think about the mother's health as well as the baby's."

Is there any T3 literature that could be helpful to share with the GP/specialist in case I get a pushback?

[humanbean]

If anyone gives you a hard time about your T3, please read this link, and print it out to show to doctors :

endocrine-abstracts.org/ea/...

and click on the orange button saying "Download ePoster" and print that out too.

[thyroid-warrior in reply to humanbean]

Love this! Thank you humanbean

[jimh111]

The few studies that claim T3 does not cross the placenta were done on afterbirths. i.e. late or full term placentas. They show high D3 (type-3 deiodinase) activity that converts T3 to T2 but D3 also converts T4 to rT3, although it prefers to act on T3.The foetus is dependent upon the mother's supply of thyroid hormones in the early stages of pregnancy. There's no evidence that the placenta has any effect on transfer of T3 to the foetus at this stage. Indeed there isn't much of a placenta during the early stages of pregnancy. Logically you would expect the placenta to regulate T3 from the mother after the baby has its own thyroid

Animals have given birth whilst on combination therapy ever since thyroids evolved. NDT has been used for over a century with no reports of pregnancy problems and is still widely used in the USA.

If it's only a matter of a day or two you may as well wait for the GP to take the blood before upping your levothyroxine dose (before getting the results).

I feel this 'advice' on T3 in pregnancy is evil. They haven't thought it through, they are just playing on fears to stop liothyronine prescribing. It puts your GP in a difficult position as they are guided by the specialists.

I would aim to keep your fT4 towards the middle of the reference interval. If your GP tells you T3 doesn't cross the placenta you can say it won't affect the baby as long as I have enough T4. I don't believe this but you are not on a high amount of liothyronine, I think high doses of T3 might cause problems. I know there have been many successful pregnancies with mothers on very high doses of liothyronine but I would be very cautious, they were exceptional cases of hypothyroidism

To state the obvious I'm not a doctor.

[thyroid-warrior in reply to jimh111]

Thanks for your insights jimh111 My plan is more to increase the T4 if needed, I feel that my current T3 dosage feels sufficient. It's in the UK that things seem more complicated - having to deal with doctors pushback and having to back up our own cases instead of looking to the doctors for guidance.

[jimh111 in reply to thyroid-warrior]

Yes, that's what I was thinking, increase LT4 if needed to get it around mid interval.

[Nat107]

hi there, my daughter had 4 miscarriages due to undiagnosed hypothyroidism, eventually turned and went to hypothyroidism so she was on levothyroxine, on her last pregnancy she did a lot of research regarding this and decided it was best for her to increase her levo by 25mcg as it was a while before her hospital appointment and she didn’t want to take any chances delaying, she was supported by her Gp, who increased it for her before receiving her hospital apt, the hospital did have a guideline for the increase but it would of been a while after she had already started it herself. So we referenced the NICE guidelines Ed and they agreed it was ok to do so.

But she was on levo only and not with combined t3. Book an appointment with your doctor asap with your concerns I would t wait to seek advice on what is best for you as with having t3 also you may need a bit levo more with it lowering your t4 levels.

There is guidelines on the NICE website and also the thyroid association but I would def seek advice asap to see what is best for you and your situation. But after my daughter having 4 miscarriages after the research and levo adjustment she gave birth to a healthy baby. Her situation may be different to yours so you need your own direction and support on increasing your Levo safely for you as I wouldn’t advise doing anything until you get your bloods taken and speaking to your own Gp first, Best wishes xx

btf-thyroid.org/thyroid-dis...

[thyroid-warrior in reply to Nat107]

Thank you for sharing  Nat107 Sounds like increment of levo is crucial for hypothyroidism. I called my GP clinic up yesterday and mentioned about my hypothyroidism and high-risk condition and requested to speak to the GP. He called back and we discussed more about my condition and he said he would refer me to the midwife (through the GP), presumably I would get a reply earlier (rather than a self-referral).

Let's see what happens after tomorrow's blood test results. Fingers crossed x

[Nat107 in reply to thyroid-warrior]

Yes it is but always seek guidance so doctor can increase your prescription for you. Best wishes x

[Star13]

Don’t need to add any advice just want to say Congrats!

[thyroid-warrior in reply to Star13]

Thank you very much 🥰