Thyroid UK

Help! Advice please re: NDT and Pregnancy

I'm now 8-9 weeks pregnant and so far had great support from my local GP and midwife service making sure I get regular thyroid function tests and they referred me to the endocrinologist.

Without meeting me the consultant at the hospital has phoned my GP and basically ordered her to switch me from NDT to Levothyroxine. The GP doesn't have much thyroid experience, and clearly admitted this, so was basically just passing on the message. I pointed out that I struggled with Levo for about three years. I never felt well on it and some symptoms were worse. My latest lab results TSH was at the low end of normal (can't find where I wrote them down now) and T4 was just under normal range. At which point I increased my dose of NDT and I have another appointment for Thyroid function test next week.

The GP explained that T3 does not cross the placenta to the growing baby and when taking NDT that lowers the amount of available T4. She said the consultant said I need to be taking at least 125mcg Levo daily at this stage in pregnancy. I asked her why I would need to increase if my T4 is in the normal range. Or if I could supplement the NDT with a low dose of Levo. After calling the consultant back she was unable to answer and just said that the consultant said that 'this was not an option' and I am 'to switch as soon as possible'

I am sure that women use NDT throughout their pregnancies, particularly in countries where it is prescribed, so just wanting to know what are the best ranges of TSH, T4 and T3 for pregnancy when taking NDT? Does anyone have direct experience of taking NDT through pregnancy? Has anyone combined NDT and Levo to slightly increase T4?

Thank you!

4 Replies

Jklm, Congratulations on your pregnancy :)

UK doctors aren't taught about NDT in medical school and I think your consultant wants you on Levothyroxine because she understands what your thyroid levels should look like on Levothyroxine which is TSH low/normal 0.4-2.0 with FT4 in or towards the top 75% of range. On NDT good levels would be low/suppressed TSH, FT4 within range and FT3 in or towards the top third of range.

I can't see the problem either if your FT4 is in the normal range. T4 is usually increased by 25-50mcg when pregnancy is confirmed. Increasing NDT by half a grain would be equivalent. Alternatively T4 can be added to NDT. Many people add T4 or T3 to NDT when the proportions of either in NDT don't suit them.

I really don't understand your GP's comment about T3 not crossing the placenta barrier. The foetus gets all it's thyroid hormone from the maternal thyroid hormone during the first trimester. I would have thought that meant it was getting T3 which had already been converted from T4 from the mother.

You could try contacting one of the American FB groups to ask about optimal levels of pregnant women on NDT. Try Hypothyroidmom or Mary Shoman.


Thank you. I've had a good look through Hypothyroidmom's pages and articles. She is very much in favour of using NDT. As are many others. Thank you for the advice about levels. I'll keep that in mind when I get my next results.

1 like

Please read this page:

It is imperative that your TOTAL (not free) T4 is at least mid-range for the baby's health. But there is no reason you can't combine T4 with a little NDT so that you feel well. If you combine medications, just make sure your combined T4 dose is at least 125 mcg, like your doctor recommends.


Thank you for the link, I think this explains better what my GP was trying to understand/explain! I hope I will be ok with NDT as I take a significantly higher dose than mentioned in the article which brings the T4 to around 125mcg daily anyway.


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