Healthy thyroid ratio?

[merlikati]

Hello,

Can't find this info anymore. How much t4 and t3 (ratio) produces healthy thyroid? Also what' s usually average ft4 level for healthy person? Is it midrange or over, under?

Just curious.



[PurpleNails Administrator]

The amount a thyroid would produce would vary between individuals, as the requirements the body uses & produces would vary greatly - but I think what you are asking is what a common FT4:FT3 ratio and it would be between 1:3.5 to 1:4.5.

Most healthy function thyroids would have mid range levels. The ranges are based on a average.

For those who take thyroid replacement most feel well with FT4 in top 3rd of range and FT3 at least half way.

It’s best to look at % of FT4 & FT3 in range - which will show if conversion is poor or good.

[jimh111]

Average (median) fT3, fT4 levels for healthy people are a little below the interval mid-points.

Ratios are misleading as the ratio changes with fluctuations in fT4 and TSH. The hypothalamic pituitary thyroid axis works to preseve T3 levels, so the ratio changes as fT4 rises and falls. I'm always wary of people who cling to ratios, I feel they don't have a good understanding of how the thyroid system works.

As for a healthy fT4 level people who are lucky enough to have a slightly higher TSH and lower fT4 live longer. I posted this topic on the subject healthunlocked.com/thyroidu... . When medicating hypothyroid people it seems obvious to me that we should aim to try and get them into the healthiest profile, i.e. with a low normal fT4 and average TSH. This requires prescribing liothyronine to bring fT3 up to normal. Doctors refuse to do this, they are unaware or the evidence (mostly) or ignore it. Levothyroxine monotherapy with a high normal fT4 carries cancer and cardiac risk and a shorter lifespan.

[Brightness14 in reply to jimh111]

I take NDT but it works well for me the ratios are way off.

[jimh111 in reply to Brightness14]

It raises the question of whether you would be well with a little less NDT and some levothyroxine - in many cases I suspect not. If we have 'simple' hypothyroidism with a failed thyroid gland it makes sense to have an initial target of supplying similar T3 / T4 amounts to what the thyroid secretes (from production of T3, T4 and conversion of T4 to T3 within the thyroid). This would restore fairly average fT3, fT4 levels.

Not all cases of hyothyroidism are simply due to a failed thyroid gland. Sometimes the pituitary is underperforming too, this has knock on effects on T4 to T3 conversion. Much of this conversion takes place in cells close to the nucleus, saturating the receptors. This isn't fully reflected in serum fT3. So, if there is impaired conversion it may be that simply restoring normal T3, T4 levels is not sufficient, the internal T4 to T3 conversion is lost. In these cases we will need additional serum fT3 to compensate for the loss of local conversion. This may not be ideal, T3 levels may be too high for some tissues and too low for others. It is what it is, until thyroid science has advanced a lot further we will have to accept that some patients need higher proportions of T3 and hence will have abnormal serum T3 / T4 ratios (not that I'm in favour of looking at these ratios).

[Brightness14 in reply to jimh111]

I agree. It's a very complex subject.

[helvella Administrator Thyroid UK]

Remember the ratios vary depending on:

The units of measurement - which must be consistent (e.g. both in mass or both in molar quantities).

Whether you look at T4:T3 or T3:T4.

My Vade Mecum has some information - basically, ranges you could see at the extreme maximum/minimum T4 and T3 within reference intervals.

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.

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.

Not everything is in this one document - my major medicines document is still separate!

From Dropbox:

dropbox.com/s/vp5ct1cwc03bl...

From Google Drive:

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

[Brightness14]

ratio of 10:1 in humans.

[pennyannie in reply to Brightness14]

A fully functioning working thyroid would be supporting you on a daily basis with trace elements of T1. T2 and calcitonin plus a measure of T3 at around 10 mcg and a measure of T4 at around 100mcg.

This is a guess estimate / a ball park :

With synthetic T3 and T4 it is said that T3 is around 3/4 times more powerful than T4 :

We will all utilise both T3 and T4 differently as our own body dictates :

Conversion of T4 into T3 can be compromised by several factors a few of which are, non optimal levels of key nutrients, any physiological stress ( emotional or physical ) dieting, inflammation, depression and ageing so you can't simply transpose a ratio without understanding a bit about body physiology .

The ranges were introduced to be used alongside Big Pharma's synthetic T3 and T4 and if you look at the base starting numbers of the T3 and T4 ranges, you may find there is a correlation there between the T3 and T4 that makes some sense as to how these ranges were decided.

[Brightness14 in reply to pennyannie]

Exactly that's why so many people are not well on NDT . Pigs have a very different ratio 4:1 With no thyroid, or gut problems and vitamins and minerals all optimal I do well on NDT. I could easily take Levo plus T3 but have chosen to stay on my NDT.

[pennyannie in reply to Brightness14]

I know - I have no thyroid and found my health restored best on NDT :

[Brightness14 in reply to pennyannie]

I am pleased that you are well, good for you.

[pennyannie in reply to Brightness14]

and ditto back to you :

[merlikati in reply to pennyannie]

So healthy thyroid produces normally 10:1 ratio as I understand not same as NDT 4:1?

[pennyannie in reply to merlikati]

That's correct - but nothing is static or cast in stone :

but we don't have a power value on any of these values of T3 or T4 compared to the natural power of one's on own T3 and T4 thyroid hormone production and the interaction between these 2 vital hormones remains a mystery.

[tattybogle in reply to merlikati]

"So healthy thyroid produces normally 10:1 ratio as I understand not same as NDT 4:1?"

not really correct , for two reasons : 1) ....an individual healthy thyroid can be quite flexible in how much T3 it produces in response to challenging circumstances. 2) ... the difference between healthy peoples T4:T3 ratios is actually quite vast fro one person to another .. so there is not really any such thing as an average healthy thyroid... we are individuals when we are healthy .. and we are individuals when we need to find the right balance of hormone replacement .. that is why one thing works for some and not for others ,and why it's so blummin difficult to get some people to feel better by following 'the rules'

... the frequently quoted phrase "a healthy thyroid produces an average 80% T4 to 20% T3" comes originally from a study by 'Pilo et al' ...... but if you look at the actual results from the 14 individuals that were used in Pilo's study .. you find this: ...... look at the vast difference between healthy person 3 and healthy person 14.

( several articles explaining the study by Pilo in detail thyroidpatients.ca/?s=Pilo+... )

14 real people

[Lovecake]

If only we all had our full thyroid panel checked way back when we were fully healthy. Then we’d know our own particular levels.But can you imagine the nhs checking everyone annually for years? Not sustainable. But I would have done it myself if I’d been told it would be really helpful for me further down the line