ft3 and t3 the same thing?

[Holiday12345]

hi is Ft3 the same thing as T3?

I think here in Scotland we only measure Tsh and t4, t3 (I think) at a push if requested but hard to get at GP. In England is it Ft3 I’ve seen on posts. That’s why I’m asking if they’re the same measurement. I’d like to know how well I’m converting and if not if I can fix that would my cholesterol maybe come down many thanks

[greygoose]

Basically, the response is: no, they are not the same thing.

T3 is actually Total T3 - although they don't seem to put the first T anymore.

There are two kinds of T3 in your blood: Free T3 and bound T3 - bound T3 is attached to a protein carrier that transports it around the body. But your body cannot use it until it is 'freed'.

Total T3 measure both the bound and the Free, but you cannot tell how much of each.

Free T3 will tell you how much T3 you have available for use by your body, so that is the more useful number.

That said, I've noticed on here that people sometimes just put 'T3' in their results when they mean FT3. But you can usually tell which it is by the range - they're totally different. Can't really give you examples off the top of my head (and we don't see many TT3s, anyway) but you learn with experience. The most used FT3 range seems to be 3.1-6.8, but it can vary a lot from lab to lab.

In England is it Ft3 I’ve seen on posts.

When the labs are done privatley, yes. But it's very, very hard to get the FT3 tested on the NHS in England.

I’d like to know how well I’m converting and if not if I can fix that would my cholesterol maybe come down many thanks

It should come down, yes. High cholesterol tends to be a hypo symptom due to low FT3.

[Holiday12345 in reply to greygoose]

Many thanks for this explanation

[greygoose in reply to Holiday12345]

You're welcome.

[radd in reply to Holiday12345]

Holiday12345

Not all hormones are bound but those that are allows control of the amount of hormone at tissue level. Binding extends the half life as the hormones must first be released to become ‘free’ and get into their target cell.

A lot of the nutritional supplements advocated on the forum are to aid the ‘free’ hormone getting into that target cell which will have receptors for that particular hormone, and initiate multiple effects.

[helvella Administrator Thyroid UK]

I've put examples of free and total reference intervals below.

We have something like 300 times as much bound T3 as free T3.

The units for bound (as shown here) are nmol/L for total and pmol/L for free.

And each nmol is one thousand times a pmol.

If you divide 0.9 nmol/L by 3.1 pmol/L you get about 290!

If you just use the numbers, and ignore the units, total is around one third (29%) free.

Total triiodothyronine 0.9 to 2.5 nmol/L

Normal adult 3.1 to 7.7 pmol/L

Reference intervals extracted from:

en.wikipedia.org/wiki/Thyro...

However, you cannot just divide/multiply to change a result from total to free or vice versa. There are many factors which mean that "300" is only approximate.

[Holiday12345 in reply to helvella]

Thank you