Pregnancy & liothyronine

[KoalaRose]

Hi guys. I need some advice urgently. I've just found out I'm pregnant, so only 4-5 weeks, but I've been doing a liothyronine trial of 2 x 10mcg daily plus 75mcg levothyroxine for the last 8-10 weeks (previously I was on 125mcg levothyroxine). I've rung the hospital to inform the endocrinologist, but I've not got a telephone appt for 2 weeks. I've been reading up and it sounds like:

- thyroid levels are extremely important early on

- levothyroxine should be increased by 25-50mcg a day

- they don't advise you being on liothyronine as it doesn't cross to the baby

Would a good course of action be to change over to 150mcg levothyroxine immediately? (25 more than I was on previously). I felt "ok" before i started the liothyronine, just still not myself even though my levels of TSH and T4 were good. I found out I was pregnant a week ago and have taken 2 x 75mcg thyroxine extra this week just to be safe in the mean time. And I have also been to have my bloods done at the hospital so the consultant has that to look at for the appt.

Thanks for any advice! Starting to worry.

[jimh111]

Have you had difficulty conceiving? It may be that the liothyronine has improved your fertility.

it is stated that liothyronine does not cross the placenta. This seems to be based on an experiment done on afterbirths, I'm using the old fashioned term because that's exactly what they were, donated placentas after birth. It seems daft to extrapolate this to pregnancy because the foetus needs mother's hormone in the first half of pregnancy, before and during the early development of the placenta. The reason I question this is that a large number of women have had successful pregnancies whilst on liothyronine only, they had little or no thyroxine in circulation. Bear in mind that for over a hundred years hypothyroid moms have been treated with desicated thyroid which contains substantial amouts of T3. I would speculate that some of these endocrinologists who claim T3 does not cross the placenta were born to mother's on NDT - they are T3 babies!

Bearing in mind I am not a doctor I would be tempted to increase your levothyroxine by 25 mcg as you are currently on the equivalent of 135 mcg levothyroxine (LT3 is 3x as potent as LT4).

[KoalaRose in reply to jimh111]

Hi, thankyou so much for replying. Yes, I do believe it is why we've conceived. Although we only really started "trying" a few months ago, but I've been pregnant both months since starting the trial (last one was a loss, obviously). I did have breakthrough bleeds between periods, which stopped as soon as I started taking the liothyronine, so I think you're right - my hormones have improved on the liothyronine immediately. I guess my question isn't about safety, it's about efficacy. If it doesn't cross the placenta then the baby won't get as much and I read it's so important early on, so that's why I'm worrying - is it why we lost the last time?

[KoalaRose in reply to KoalaRose]

Oh I should also add - my GP did check my hormones due to the breakthrough bleeds and said I was heading towards menopause 😶 I mean, not hugely surprising as I'm 37 and my mum went through it early 40s, but still! I do wonder what my levels look like now seeing as I didn't struggle after starting the liothyronine

[greygoose]

I agree with jim. It's another one of those weird ideas doctors get with no proof that it's true. They are just so scared of T3 - because they don't understand what it is - that they will do anything to put people off taking it.

They also say that T3 can't cross the blood/brain barrier. But those of us on here that take T3 only haven't turning into dribbling imbeciles yes! We're still managing to think and post on the forum.

Besides, what about pregnant women who don't have thyroid problems. Their thyroids are churning out T3 all the time, and their T4 is being converted into T3 in their cells with no untoward effects on the baby. If T3 were dangerous, the human race - and most animals - would have died out long ago!

[KoalaRose in reply to greygoose]

Thanks for replying. Yeh, it's not the safety that worries me at all actually - I haven't read anything to that effect? It's more the effectiveness compared to T4. If I can manage on T4 alone but up my dose, would this be better for baby? I know I've only got 2 weeks to wait before I talk to the endocrinologist, but it's so important in the 1st trimester and by the time I've talked to them, made the change and that change takes effect I'm gonna be well towards 2nd trimester 🙈

[greygoose in reply to KoalaRose]

If I can manage on T4 alone but up my dose, would this be better for baby?

Why would it be? As jim said, there's no proof that T3 can't cross the blood placenta barrier. And, if you have good high levels of T4, the T3 is not going to stop that going through, it'll cross over anyway. Plus you have to think about your own health so that you're strong enough to give birth and then take care of your baby, and for that, YOU need the T3. So, personally, I would carry on taking it.

[KoalaRose in reply to greygoose]

Thankyou! So best bet is to up my T4 to 100/day and keep on the T3 also?

[greygoose in reply to KoalaRose]

I would think so, yes.

[FallingInReverse]

I find this article as another source of info for you to take into consideration as you do your research:

drugs.com/pregnancy/liothyr...

[FallingInReverse]

And this recent reply (with an article link for a study on Levo increases during pregnancy) will be helpful:

healthunlocked.com/thyroidu...

[jimh111]

It looks like T3 doesn't cross the placenta in the late stages of pregnancy. About half way through pregnancy the baby makes its own hormone. I don't have evidence but logic tells me the baby wouldn't want to get too much T3 from the mother late in pregnancy in case it became thyrotoxic. As greygoose points out all babies are carried by mothers with T3 in their bloodstream, whether it comes from tablets or the mother's thyroid.

I read up on this late last year but have forgotten most of it! The thyroid secretes about 6 mcg T3 so it is possible that doses above this might carry a slight extra risk to the baby - it's also possible that levothyroxine monotherapy also carries a risk. Nobody knows. We do know that NDT was used for over a century delivering much higher T3 (and T4) doses than you are on and there are no reports of increased risks. So we can assume any potential risk either way is small.

[greygoose in reply to jimh111]

It looks like T3 doesn't cross the placenta in the late stages of pregnancy.

Wouldn't that be true of T4, too, once the baby has its own thyroid?

Also, I have read that if the mother is short of thyroid hormone, she will take it from the baby, leaving the baby with low levels. Have you come across that?

[jimh111 in reply to greygoose]

The late term placenta expresses lots of D3, type-3 deiodinase, which converts T4 to rT3 and T3 to T3. It's preferred substrate is T3. This means it preferentially converts T3 to T2. So, D3 effectively stops T3 crossing the late term placenta. What happens in early pregnancy isn't clear, the placenta doesn't become fully functional until around month five.If (excess) T4 crosses the placenta in late pregnancy the baby should be able to mitigate any effects by reducing its own secretion of hormone and converting less T4 to T3. Even so hyperthyroidism carries risks to the baby.

I've heard that if the mother is short of thyroid hormone she will take it from the baby but I've never seen any evidence to back it up. I think this was speculation that came about long before our limited understanding of how thyroid hormones cross the placenta.

[greygoose in reply to jimh111]

OK, thank you for that explanation.

Yes, there are far too many speculations taken as fact, which get embedded into protocol - even when they turn out to be wrong! It's time someone set about more research into all things thyroid because hypo lives matter, too!

[KoalaRose]

Thanks so much everyone. Feeling much more reassured. I'll definitely be back if I need more advice and maybe even one day giving some of my own 😊

[humanbean]

The connection between mother and fetus lets T4 and T3 from the mother reach the fetus early in pregnancy and while the placenta is doing its job. One of those jobs is to filter out thyroid hormones from the mother by (very roughly) middle of the pregnancy when the baby's thyroid has started to function and the baby's pituitary and hypothalamus (which control the thyroid) are able to do their jobs.

You might find these two links of interest - and it would be a good idea to print them out in case your use of T3 is questioned. Some women have been told by medical staff that T3 will cause miscarriage or kill their babies, which is a load of tosh.

endocrine-abstracts.org/ea/...

endocrine-abstracts.org/ea/...

[FallingInReverse]

What’s your latest FT4 result, and TSH and FT3, with ranges?

[KoalaRose in reply to FallingInReverse]

I'm not actually sure as it was done at the hospital and I was told the results over the phone. They were within range, but that was also before I started the T3. I know that my vit D was a little low so I've made more of a conscious effort to not forget to take it now 🙈. I went in for a blood test yesterday though - I'll come back when I have the results 😊