Is fT4 too low?

[hose1975]

Currently taking 150 mcg T4 and 22.5 mcg T3 daily.

Latest bloods have returned results of TSH 0.03, fT4 11.4 (10.8-19.8) and fT3 5.2 (3.5-6.5).

Previously fT4 was closer to 15, having fallen from 20-odd when I started taking T3.

I have gained quite a lot of weight recently, partly because of taking quetiapine for bipolar disorder.

Does anybody have any idea why my fT4 has fallen now, and should I be looking for it to be a bit higher?

Many thanks

Jo

[silverfox7]

Results are read differently when taking any form of T3. So TSH will be suppressed, FT4 can fall but FT3 should be high in the range but never over.

So the only accurate reading is the FT3.

So results are where I would expect them to be. My TSH is 0.01 but how you are feeling is more important. There is a little room to take more medication but if you are feeling well leave it.

Are you taking the new medication well away from your thyroid meds?

If you are taking it well away from your thyroidxmeds and due to weight gain you may want to try adding in a very small amount of T3 but I take NDT so not familiar how to juggle adding in T3.

[hose1975 in reply to silverfox7]

Thanks for your reply. Yes, thyroid meds are all taken in the morning, quetiapine just before bed.

[SilverAvocado]

I've heard people's say that freeT4 will sometimes drop when you introduce T3, but I'm not too sure. It seems to be what has happened to you. Have you not reduced T4 dose at all since it was 20-ish?

Theoretically freeT4 levels make no difference, as long as freeT3 is good, because T4 is just for storage in the body. However some people are sure they need good levels to feel well. But I think that's something quite low on the list to look into.

Your freeT3 is low-ish, and that may be why you're having symptoms. Most people feel well with it close to the top of the range, into the top third. You've got quite a bit of room for an increase.

If you've had a recent change in symptoms vitamins are worth looking into, ferritin, folate, vit B12, vit D, to see if they've dropped.

[hose1975 in reply to SilverAvocado]

No, my T4 dose has remained unchanged since the introduction of T3.

All vitamins and minerals in a healthy range ATM.

[SilverAvocado in reply to hose1975]

I'd definitely pursue getting a T3 increase if I were you. See if you feel better with a freeT3 near the top of the range.

[hose1975 in reply to SilverAvocado]

As I understand it, blood results for T3 should be at around 80% of the range tops (to allow for its peak to be still within range). This would mean a level of 5.9 for me with the local range. I may try an additional 6.25 mcg and see how I feel.

[SilverAvocado in reply to hose1975]

I think it's definitely worth trying if you still have symptoms. There is no one-size-fits-all, I think 80% is very specific, as it's possible any one of us could be a bit more unusual! The top of the range is there for a reason, so it's alright to go all the way up to it, and if symptoms justify it even over the top.

[Angel_of_the_North]

FT4 often falls when you take t3. That result would be fine for me, but others need it higher

[hose1975 in reply to Angel_of_the_North]

Thanks for your reply. I think it's more a question of *why* the fT4 has fallen again (from 15-odd to 11.4), given that I've been taking the same dose of both T4 and T3 for some time now.

[Angel_of_the_North in reply to hose1975]

When I went on to T3 only, it took 2 years for FT4 to drop from near top of range to near bottom, then it stayed steady. So I don't know why it happens without a dose change, but it does.

[GKeith]

Everyone is different; I take 50mcg of T4 and 30mcg of T3 and feel quite well.