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Total thyroidectomy and pregnancy questions

Anyone here who had total thyroidectomy BEFORE pregnancy ? Or knows more about maternal and fetal thyroid hormone needs during pregnancy (especially during the first trimester)?

If yes, here are some questions I have:

1. Why are there different ranges for normal FT4 in pregnant and non-pregnant women? (I'm interested to know if the pregnancy ranges apply to levothyroxine-dependent women, too).

2. Does the fetus has priority on maternal T4 during the first trimester?

3. Is TSH's value important for maternal or fetal health? (I was in the scenario high TSH, normal FT4 during the first 2 months).

4. How does folic acid intake impact Euthyrox (levothyroxine) absorption if taken shortly (30-60min) after Euthyrox intake?

If you have an answer to any of my questions, I would be grateful for it. I was doing a lot of research lately on this topic, but couldn't find precise answers.

12 Replies

Welcome to the forum, Clauditza.

TSH >3.0 can make conception difficult and increases the risks of miscarriage, preterm births and postpartum psychosis. The low-normal range 0.4-2.0 with FT4 in the upper range is recommended for women planning conception and newly pregnant in the UK and pregnant women are usually advised to take Levothyroxine only.

The foetus is dependant on maternal thyroid hormone until it develops its own thyroid gland at approximately 12 weeks.

Take Euthyrox 2 hours away from folic acid and other supplements as they may reduce absorption of Euthyrox.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

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So its not possible to treat only with T3 until the baby will be independent??? Or its ok to have a pregnancy with t3 only??

Many thanks clutter



I've not seen any information on treating pregnant women with T3 or NDT.  UK doctors seem to ask pregnant patients to stop T3 and take T4 only during the pregnancy.


Thank you for your answer, Clutter!

When you say FT4 in the upper range, what range are you talking about? The one for pregnant or non-pregnant considering the mother had previously a total thyroidectomy ?

Also, do you know if the foetus could have been affected if the TSH was high (14.84), but the FT4 was in the normal (upper) range?

Is it possible that even though the FT4 was normal, the high TSH is an indicator there was not enough was not enough T4  for the baby during the first trimester, too?

My pregnancy went fine, I have already delivered the baby and she seems fine by now (she's 13mo), but I'm trying to find out whether there are any chances that her brain development could have been impacted at all by the high TSH and see the effects later in life.



There isn't a separate  FT4 range for pregnancy so FT4 will ideally be in the top quartile of range.

High TSH is usually an indication of low FT4.  There is evidence that low maternal FT4 may cause lower IQ and learning difficulties in children.



This article suggests that improving FT4 during pregnancy negates adverse effects of low FT4 during the first trimester:


Maternal   hypothyroxinaemia   during

early  gestation  is  an  independent  determinant  of  a

delay in infant neurodevelopment. However, when fT4

concentrations  increase  during  pregnancy  in  women

who  are  hypothyroxinaemic  during  early  gestation,

infant development appears not to be adversely affected.


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Clutter, thank you for the links above.

As for the FT4 range, my lab has the following values:

Adults: 12-22pmol/L


1st trimester: 11-19 pmol/L

2nd trimester: 9.7-17.5 pmol/L

3rd trimester: 8.1-15.3 pmol/L

This happens in Belgium and maybe the values depend on the lab, but I found that there are pregnancy specific ranges in the UK, too: thyroiduk.org.uk/tuk/guidel...



FT4 ranges aren't standardised and vary across the UK which is why advice is generalised to having FT4 "in the upper range".

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I have one more question: Do you know how much is the absorption rate reduced when folic acid is taken less than 2h away from Euthyrox ?



I've no idea.


i would do some reading on the website hypothyroidmom, for pregnancy information and all about proper levels of t4 and t3 and make sure that you really need a thyroid removal before it is done.


I had Graves before the thyroidectomy and after several years of treatment it kept coming back. Anyway now it's gone, so there's not much to be done on this side.


Good luck. I had one child after my TT. I needed a lot of monitoring and I had to be on the ball re prompting doctors for tests and results and interpretation but it was all worth it! Sue


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