Thyroid UK

No increase in FT4 with either Levo or NDT. Second miscarriage- ? connection

I wonder if anyone can help me. I have just had my second miscarriage at 11 weeks pregnant. The first one was at 9 weeks, which I attributed to my thyroid as my TSH was 3.12 at 6 weeks gestation. I started Levo, but I think this was too late as this was only started at 7 weeks gestation. After the miscarriage, I continued on the Levo and the TSH went right down but the FT4 remained at 12-14 max (range: 9-23 pmol/L). After the miscarriage, I became progressively more unwell with hair loss despite the Levo and I required several short syacthen tests for reduced cortisol production which showed reduced production. I was never started on cortisone as the adrenal function gradually improved, however my GP and Endo here in the UK could not offer an explanation as to why I continued to feel like death and wanted to sleep all day, saying my bloods on Levo were fine.

In desperation, I visited a functional medicine specialist in the US in late 2015, who advised NDT (NatureThroid). This has helped me tremendously, and just after my most recent miscarriage a month ago, TSH was at < 0.01 (range 0.3-4.2 mIU/L

), FT4 at 12.6 (range: 9-23 pmol/L

) and FT3 at 4.9 (range: 2.5-5.7 pmol/L). My FT3 was 5.6 at conception.

I am keen to try to get pregnant again asap, but don't want my thyroid to be the underlying cause and risk another miscarriage. I understand that TSH is often suppressed with NDT and that FT4 is reduced due to the FT3, but my question is: why did my FT4 not go up even with just T4 treatment (Levo) even though the TSH went down? Should FT4 be raied to sustain a healthy pregnancy?

Any ideas gratefully received- I am at my wits end trying to work things out!

Thanks so much in advance

4 Replies


I'm very sorry for your loss.

The foetus is dependent on maternal thyroid hormone until it develops its own thyroid gland at around 12 weeks. Hypothyroid women planning conception should have TSH in the low-normal range 0.4 - 2.5 and Levothyroxine dose should be increased by 25-50mcg when pregnancy is confirmed.

TSH drops because sufficient FT4 is detected. I don't know why FT4 didn't rise. FT4 12 or 14 in range 9 -23 isn't low and is unlikely to be why you miscarried.


Many thanks Clutter!


Very sorry for your miscarriages.

Just a thought, do you know if you have had thyroid antibodies checked? There are two sorts TPO Ab and TG Ab. (Thyroid peroxidase and thyroglobulin) Both need checking, if either, or both are high this means autoimmune thyroid - called Hashimoto's the most common cause in UK of being hypo.

TPO is rarely checked and TG almost never checked. More common to have high TPO or high TPO and high TG, but negative TPO and raised TG is possible, though much rarer. There are a few members on here that have this, often they have struggled to get diagnosed.

If you have Hashimoto's then you may find adopting 100% gluten free diet can really help reduce symptoms, and lower TPO antibodies slowly over time too.

Selenium supplements can help improve conversion of T4 to T3 and may also lower antibodies


Thanks so much Slow Dragon. I have had antibodies done on NHS, which is negative but I know the other one needs doing- probably privately. I have read that even negative blood tests, however, does not exclude Hashimoto. I have gut issues and have eaten gluten free for 8 years now. Plus have had adrenal issues, so all in all an autoimmune picture which would def tie in with antibodies. I'll def look into having those done. Thanks again


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