Low TSH but T4 and T3 now normal

[Amuia]

Hi, have been on 100mcg levo for the last 2 months for hyperthyroidism (gradually upped from 50mcg when diagnosed in May).

I've posted a few times on here, lots of helpful advice!

Just done a private blood test this week (in between GP blood tests every 6 weeks) to check T3 and T4, results:

TSH 0.16 mu/L (0.27 - 4.2 mU/L)

FT4 16.3 pmol/L (12 - 22 pmol/L)

FT3 4 pmol/L (3.1 - 6.8 pmol/L)

Realise my TSH is now a bit low (blood test was first thing and 24 hours after last dose etc.) byt T3 and T4 finally look good!

I imagine that the GP might want to reduce my dose at my next GP blood test if it's still low (3 weeks ago TSH was 0.08mu/l). Have previously checked Vits and B12 etc and they are all normal. Feel pretty ok at the moment too!

GP only ever tests TSH - should I share the above with them?

Is it better to have low TSH if T4 and T3 are normal?

[fuchsia-pink]

Yes!

TSH may be a useful primary diagnosis tool in establishing thyroid problems, but is pretty irrelevant once you're on meds (except that GPs, comfortable in their ignorance, obsess about TSH)

You say you feel ok - but do you feel completely well or just not brain-foggy and exhausted? If not tip-top I'd say you should be asking for a dose increase - and def decline a reduction. Your free T4 is only 43% through range and free T3 only 19% through range ... I'd want both to be much higher myself - at least 2/3 through range and probably higher x

[Amuia in reply to fuchsia-pink]

Thanks for the quick reply - when I say ok you're right, still not 100% so thanks for the input! 👍

[SeasideSusie Remembering]

Amuia

Hi, have been on 100mcg levo for the last 2 months for hyperthyroidism (gradually upped from 50mcg when diagnosed in May).

I just wanted to point out your typo, it is in fact hypOthyroidism nor hypERthyroidism

TSH 0.16 mu/L (0.27 - 4.2 mU/L)

FT4 16.3 pmol/L (12 - 22 pmol/L)

FT3 4 pmol/L (3.1 - 6.8 pmol/L)

Realise my TSH is now a bit low (blood test was first thing and 24 hours after last dose etc.) byt T3 and T4 finally look good!

It doesn't matter what they look like, it's how you feel. Your FT4 is 43% through it's range and your FT3 is 24.32% through it's range. These are the actual thyroid hormones (TSH is not a thyroid hormone, it's a pituitary hormone) and it's these that tell us our thyroid status. Your levels are, in fact, rather low for someone on thyroid hormone replacement, many would not feel well with these low levels. However, if you feel good with them at this level then that is fine for you.

I imagine that the GP might want to reduce my dose at my next GP blood test if it's still low (3 weeks ago TSH was 0.08mu/l).

In fact 0.16 is higher than 0.08 (0.16 is closer to 1, 0.08 is closer to zero).

Dose adjustment should never be by TSH, doctor should look at the FT4 and FT3, it's the FT3 that's most important but unfortunately they're never taught that.

Have previously checked Vits and B12 etc and they are all normal.

Normal just means "in range", it's optimal levels that we need. Recommended levels are:

Vit D - according to The Vit D Society and Grassroots Health - 100-150nmol/L with a recent blog post on Grassroots Health recommending at least 125nmol/L

B12 - Active B12 over 100 or Total B12 top of range

Folate - at least half way through range, if no range then double figures

Ferritin - half way through range with some experts saying that the optimal level for thyroid function is 90-110ug/L.

GP only ever tests TSH - should I share the above with them?

Definitely, especially if he wants to lower your dose. Lowering your dose will reduce your FT4 and possibly FT3 levels which will give you hypo symptoms. If this is a MonitorMyHealth test you can point out that it's an NHS lab at Exeter Hospital so they should be acceptable, if he wont accept them then refuse to lower your dose (as you feel good at the moment) unless he gets FT4 and FT3 tested as well.

Is it better to have low TSH if T4 and T3 are normal?

Nobody can say what's better for anyone, you have to find out yourself where your sweet spot is. It's often the case that TSH is low when our FT4 and FT3 levels are optimal for us.

[Amuia in reply to SeasideSusie]

Apologies, typo, def hypO! That's all really helpful, thank you. It was a monitor my health test so that's good to know and lots of advice when I next speak to the GP!