Explain in a succinct way the meaning of all the Thyroid function jargon

[Suffolklady]

I know I should know all this but I can’t get my head around the T3, T4, FTs TSHs blah blah blah and what each does and what they should do. To absorb the technical is hard to understand and get to grips with so a simplified version of what these mean would be helpful to me. Thankyou.

[DippyDame]

This might help!

thyroiduk.org/thyroid-funct...

[Suffolklady in reply to DippyDame]

Thank you Dippy Dame it’s very involved with all the different measurements and the what ifs and where fores I’ll have to read it over several time

[tattybogle]

TSH ( Thyroid Stimulating Hormone) is a message from the brain to the thyroid , to ask for more ( or less ) thyroid hormone (T4 & T3) to be made.

Think of TSH and T4/T3 as being on opposite ends of a see-saw :

If T4 /T3 go low (hypothyroid), the TSH goes high.

if T4/T3 go high (hyperthyroid) , the TSH goes low.

fT4 (Free T4) is the name of the lab test used to measure how much T4 is a 'feely ' available (the rest of it is 'bound', if you wanted to measure all of it together you would use a TT4 test ~Total T4)

Same for fT3 (Free T3) fT3 test shows what is freely available , and TT3 shows all of it.

Does that help ?

[Suffolklady in reply to tattybogle]

Yes it’s getting there. What is the difference between T3 and T4 and what does conversion mean? Sorry to be such a numpty.

[SeasideSusie Remembering in reply to Suffolklady]

Suffolklady

T4 is a pro hormone and it has to be converted to T3 which is the active hormone that every cell in our bodies need. Lack of T3 is what causes symptoms and, ultimately T3 is what keeps us alive.

The thyroid itself produces some T3 (as well as T4) but the majority of the conversion takes place in other organs - mainly in the liver, but also take place in cells of the heart, muscle, gut, and nerves

[tattybogle in reply to Suffolklady]

T4 is the long life/ storage / transport form of Thyroid Hormone ... it doesn't fit into the keyhole at the centre of your cells , so it can't 'do' anything until the cells 'take it out of the tin'.

T4 has 4 iodine atoms ( hence T4) ...We describe T4 is 'inactive' (which isn't totally correct but it will do for now ) .

once inside the outer walls of your cells, the de-iodinases remove one iodine atom to 'convert' it into T3 (3 iodine atoms ).

T3 will then 'fit' into the keyhole (Thyroid Hormone Receptor) and make the cell do whatever that cell does. So we describe T3 as 'active'.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

it's more complicated than that obviously .. and there are several other things happening all at the same time, it's not just a simple one way street.

The thyroid mainly produces T4, but it also produces a bit of 'ready made' T3, (and the ratio of T4/T3 that is produced by the thyroid can change in response to need.)

T4 and T3 (from the thyroid) go round to all the cells in the blood ... those cells use up some of the T3 they have converted from T4 , they also put some T3 back into the blood to go round again.

T4 has a 'half life' of about 7 days in the blood .. meaning after 7 days, half of it is gone .. after another 7 days half of the remaining half is gone .. and so on .. so you can see it is a very useful long term store which allows the cells in the body to draw on it to convert it to T3, as and when they need to .

T3 has a much shorter half life in the blood (? about 2 /3 days ~ i've forgotten exactly how long )

[greygoose in reply to tattybogle]

The half-life of T3 in the blood is about 24 hours. But the T3 that gets into the cells stays there for about 3 days.

[tattybogle in reply to greygoose]

Ta x

[greygoose in reply to tattybogle]

[SlowDragon Administrator]

Levothyroxine is T4

We MUST convert Ft4 into FT3 before can use it

Many people find, especially after menopause or years on just levothyroxine that conversion rate gets worse

So it becomes harder to convert Ft4 into Ft3

GOOD vitamin levels help improve conversion rate

Low vitamin levels are very common when on only levothyroxine, especially as we get older

So for good Ft3 levels we need

1) Measure Ft4 -

Test thyroid levels early morning and last dose levothyroxine 24 hours before test

On JUST levothyroxine Ft4 needs to be at least 70% through range

2) Measure Ft3

If Ft4 is high in range and Ft3 is low this shows poor conversion rate

3) Measure Vitamin D, folate, B12 and ferritin

These need to be at good levels

Vitamin D at least over 80nmol

Serum B12 at least over 500

Folate and ferritin at least half way through range

[DippyDame]

None of us know much about thyroid function until we are faced with having to understand it in order to improve our health! It's easier to get there if we take one step at a time....and that is probably by first looking at thyroid testing

A full thyroid test includes...

TSH, FT4, FT3, vit D, vit B12, folate, ferritin and thyroid antibodies TPO and TG. The latter test for thyroid autoimmune disease/ Hashimoto's

The NHS tend to rely on TSH, sometimes with FT4, but rarely with FT3. Yet according to science, FT3 is the most important reading followed by FT4

T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood. Free T4 is the thyroxine that is not attached to a protein in the blood.

The thyroid gland produces about 20% T3 and 80% T4

T4 is converted to T3, the active form of thyroid hormone, by enzymes called deiodinases.....this, in various tissues of the body but mainly in the liver

Conversion may be impaired by a genetic polymorphism revealed by a Dio2 genetic test.

Comparison of FT4 with FT3 - high FT4 with low FT3 -normally indicates poor conversion.

If conversion is poor then the addition of a little T3 usually helps as does optimising the nutrients listed above.

Unfortunately medics are frequently reluctant to prescribe T3 ....that is another saga!

I have a rare condition that requires high dose T3-only. Like many others I have to buy my T3 from abroad.

To become active T3 must reach the nuclei of the cells via T3 receptors....so receptors also need to function correctly

For good health almost every cell in the body requires T3 in an adequate and constant supply. For most people the system works well.

TSH is a pituitary hormone it is a signal to instruct the thyroid to produce more or less hormone. It refects the total amount of thyroid hormones detected in the blood ....high TSH, more hormone required from thyroid gland; low hormone, less hormone required! But crucially TSH does not shown the level of each individual hormone (T4 and T3)....and here we have a further saga!

The TSH test was initially devised to diagnose hypothyroidism by way of a high TSH test result . It has since been tweaked and is now controversially used to monitor and adjust hormone levels.

Science proves TSH is not a reliable marker and often results in poor diagnosis and on-going symptoms.....and the reason many patients arrive here.

This might help!

[Hidden in reply to DippyDame]

None of us know much about thyroid function until we are faced with having to understand it in order to improve our health!

Bonkers, isn't it? Considering how vital the thyroid is... I could tell you where my heart & lungs are but wouldn't have had a clue about where my thyroid was until a few years ago!

[Suffolklady]

Thank you for all your advice on the subject I will carefully read through and digest much appreciated everyone’s advice and knowledge.

[Charlie-Farley]

Get a good book - one recommended on Thyroid UK and have a read. Read other people’s questions, stories and lived experience- this is by far one of the best ways to get to grips with the subject. I’ve been reading regularly for well over a year now and it’s sinking in. It’s wholly worth it and we simply have to be our own health advocates when the understanding in the medical profession is as woeful as it is at present.

[helvella Administrator]

My vade mecum is very much NOT an introduction, a simplified approach. But what it does is provide a place to look things up.

If it is in there, there might be sufficient information. Or a link to more information. Even the abbreviations and acronyms alone might be helpful.

helvella - Vade Mecum for Thyroid

The term vade mecum means:

1. A referential book such as a handbook or manual.

2. A useful object, constantly carried on one’s person.

Please don't get put off by the number of pages!

Nor by the fact it is targeted at people interested in thyroid issues. Much of its contents could be of use to many involved in health issues. Things like abbreviations, lists, general reference information, an Appendix of links to many useful websites.

And do keep up to date. I edit it frequently- sometimes trivially, sometimes extensively. If your copy is more than a few weeks old, please download it again. (You must download - not just view in a browser- for the Table of Contents to work.)

In particular, it is not intended that you sit and read the document. Just that you download it and know you can look things up.

If there is anything you'd like me to add, let me know.

From Dropbox:

dropbox.com/s/vp5ct1cwc03bl...

From Google Drive:

drive.google.com/file/d/1P9...