FT4, how does this work?

[TappedOut]

Hi All,

You know how the literature and experiences tell us that FT4 should sit midrange and FT3 in the upper third of range? In light of this understanding, I'm confused as I have also read that upon proper thyroid treatment, the FT4 goes down. Can you clarify? I'm confused because. My FT4 has gone down since I began NDT, but it was never midrange and I'm not sure if I'm improving with medication or not. My symptoms are essentially unchanged. When should FT4 be midrange? When should it drop? My range is .82 - 1.77. Mine was 1.13, and is now .9

❤️TappedOut

[greygoose]

It should always be higher than mid-range when on T4, and, ideally, the FT3 a bit higher. FT4 at mid-range would be a bit low.

However, when taking NDT, or straight T3, the FT4 will drop because the body only hangs on to what it needs, and it doesn't need as much.

The FT3 is always the most important number.

[TappedOut in reply to greygoose]

Ohhhh. Ok. That's what I missing in my analysis. The difference between what's expected in FT4 is based on wha one is taking- NDT and or t3 as opposed to t4. Taking t4, t4 should be mid. Taking NDT or t3, t4 will go down based on bodily need. Got it.

Thank you Greygoose!!

[greygoose in reply to TappedOut]

You're welcome. But, ideally, FT4 should be higher than mid-range when taking T4 only.

[Angel_of_the_North in reply to greygoose]

I think around 75% of range for most people on levo only. So on your range, about 1.5 if on T4 only. 50% of range is about 1.2 so you were way under half way (around 32.6%).

[TappedOut in reply to Angel_of_the_North]

Hi AngeloftheNorth, thank you for your reply.

I understand what you're saying....I'm on NDT and a member here noted that w/NDT and or T3 treatment, the t4 is expected to go down. Have you heard this as well?

[Angel_of_the_North in reply to TappedOut]

I've seen in it myself.

[TappedOut in reply to Angel_of_the_North]

What's that Angel, you mean you took NDT or t3 and it lowered your t4? How are you overall? You still take t3 or NDT, if I may ask?

[Angel_of_the_North in reply to TappedOut]

T3 only. Feel pretty much OK. FT4 dropped from about 60% of range to under range over several years, but I felt better (even though Ft3 actually isn't much higher).

[TappedOut in reply to Angel_of_the_North]

Oh that's so good to hear that you're feeling relief. Thank you so much for your help. Something is giving me the jitters, like an adrenal rush, coffee feeling. I'm not really on much NDT but I don't know if it's t3, t4, or my low ferritin that's causing this feeling. Some say it's bc I'm not titrated up enough, but I can't imagine taking more of this feeling gets worse with every slight increase.Ughhhh....