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Update on recent blood results borderline hypo trying to conceive

Hello again,

I have recently had my 8 week blood results back after starting lyvothyroxine 25mcg. My TSH level was down to 3.4 and free T4 at 16. (Blood draw taken at 9am without having taken medication/breakfast).

My initial blood results in August were;

Serum TSH level 4.9 mu/l (Reference range 0.30- 6.00mu/l)

Serum free T4 level 13.9 pmol/L (Reference range 10.00- 22.00 pmol/L)

I saw a fertility doctor after having 1 miscarriage in Feb who suggested that there was evidence that getting the tosh below 3 may assist response to fertility treatment. I don't plan to have any fertility treatment, I just wanted to establish if there was an underlying cause for miscarriage before trying again.

My questions are;

- should I push for a further dose increase to 50mcg to get my TSH levels to below 3?

- if I was to begin to take 50mcg how long would it take to get my tsh below 3?

- I am hoping to start trying to conceive asap- I have heard the free T4 is the relevant number for the foetus - is my level sufficient for this?

- as I was only ever a borderline case of hypothyroidism- my understanding is that the nice guidelines re sub clinical hypothyroidism and trying to conceive don't apply- is sub clinical and borderline the same thing?

- I have been told fertility doctors and IVF doctors like the tsh below 2 before starting treatment- does this 'optimum' apply to the normal population or just those seeking IVF etc

Thank you so much in advance for your help i really appreciate any advice you can give me

Thank you

8 Replies

Also- I tested negative for thyroid antibodies


Your blood hormone levels are quite normal and you don't have a lot of hypothyroid symptosm. However, taking levothyroxine whilst keeping your TSH above 0.3 and fT4 below about 20.0 is quite safe and cheap. Given all the other fertility options are much more expensive and risky it seems reasonable to go to 50 mcg and if you conceive keeping your TSH below around 2.5. This is a bit of an unknown area, I don't see why they can't try this and perhaps wean you off the levothryoxine after six months or a little while after pregnanacy.


Thank you. I really don't want to be on lyvothyroxine forever and recently found out that a blood result from 10 years ago showed my TSH was 6.3 so it's seems to be improving (perhaps due to lifestyle changes) as opposed to getting worse as the general consensus seems to suggest. If I was to get pregnant now with a tsh of 3.4 do you think this would be particularly risky in person otherwise healthy? Thanks for your reply


I don't think so but I'm not a doctor. I'm just going by studies that tend to show an increase in risk with elevated TSH but these are relative risks and the absolute risk I believe is low. I'm now going beyond my knowledge.

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Ask for a dose increase. Women planning conception should have TSH in the low-normal range 0.4 - 2.5. Having TSH >3.0 can make conception difficult and increases the risk of miscarriage. When pregnancy is confirmed it is usual to increase dose by 25-50mcg to ensure good foetal development.

NICE recommends hypothyroid women planning pregnancy should be referred to endocrinology for management. cks.nice.org.uk/hypothyroid...

Management of primary hypothyroidism: statement by the British Thyroid Association Executive Committee

13. The serum TSH reference range in pregnancy is 0·4–2·5 mU/l in the first trimester and 0·4–3·0 mU/l in the second and third trimesters or should be based on the trimester-specific reference range for the population if available. These reference ranges should be achieved where possible with appropriate doses of L-T4 preconception and most importantly in the first trimester (1/++0). L-T4/L-T3 combination therapy is not recommended in pregnancy (1/+00).


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Thanks clutter but would i be considered a ‘hypothyroid’ woman planning a pregnancy? Do my figures mean i am considered hypothyroid? Or just that i am borderline with slightly raised TSH?


My endocrinologist recommends TSH being in the 0.3-2.0 part of the normal range. If you get pregnant you may need to increase your does to stay in this range. The reason is that the baby has no thyroid until about wk 12 so they are depleting your stocks and if you don't have enough they will suffer hence risk of early miscarriages. My endo recommended already being in that low part of the normal range before conception because that increased need for the baby is needed before you would even know you're pregnant (ie. before you miss your period). I was also "borderline" "sub-clinical" hypothyroid but I do have Hashimoto's.

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Hi all! Further update! My GP prescribed me a further 12.5mcg so i am now on 37.5mcg! She doesnt want to give me the 50mcg yet! What do you guys think? Will my current TSH go down from 3.4 on this tiny increased dose? The pharmacist gave me the 25mcg as they didnt have the 12.5 in stock so i am deliveberating whether to just take the extra 25mg each day.



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