How much T3 and T4 released by healthy thyroid?

[ak_83]

I'm trying to get back to basics as I think I've been overdosing on my mix of thyroid impacting my adrenals.

How much T3 and T4 released a thyroid of a healthy human male? Is it 100 T4 and 20 T3 or am I misremembering something I've read before?

[greygoose]

It doesn't really matter how much a healthy thyroid makes, because you don't have one. Hypos often need more hormone than a euthyroid person. And, you have to find out how much you need by trial and error. How do you feel? And when did you last have labs?

[ak_83 in reply to greygoose]

Sure. But how much is the ideal level? I just would like to know...

[greygoose in reply to ak_83]

There isn't a universal 'ideal' level. We're all different and we all need what we need.

[tattybogle]

The t4/t3 ratio ,and amounts in healthy people are actually enormously varied, we all have our individual setpoints for TSH/T4/T3 in health, and these are much narrower than the wide normal ranges that include everyone.

I was surprised to see how much T3 /T4 ratios differ in individuals, and it doesn't seem to be a male /female thing, it's just a "i'm different to you" thing .

You may find help understanding why it's so difficult , (and pointless) to trust that "average levels" will work for an individual amongst these articles from a respected canadian thyroid patients website. :-

I can't remember off the top of my head which article out of many had the best diagrams of the varied T4/T3 ratios found in healthy folk, so i'll put a few links , but have a look round the rest of the site if you don't find what you are looking for on these:-

thyroidpatients.ca/2020/05/...

thyroidpatients.ca/2019/10/...

thyroidpatients.ca/2020/08/...

thyroidpatients.ca/home/sit...

[Marinaaa in reply to tattybogle]

thanks very much for this really valuable information. Very interesting and wide-opening.

[ak_83 in reply to tattybogle]

Thank you. I'll take a look at this.

[qvacuum]

Interesting and relevant question! It apparently depends on body weight and physical activity. The scientific literature gives slightly varying numbers (which makes sense due to individual variations). Typically, there seems agreement on the production rates for a healthy human (for a 70kg person):

T4: ~100 mug/day [track runners: ~120 mug/day]

T3: ~32 mug/day

But only about 20% of T3 is produced in the thyroid, hence about 7 mug/day, the rest is produced in tissue from T4, assuming healthy conversion from T4 to T3.

What do these numbers imply for substitution doses? It obviously depends on absorption rates. Literature quotes a max. of 80% for T4 and 95% for T3. Now one can do the math. Under optimal absorption and optimal conversion from T4 to T3, the substitution should be about

T4: ~ 100 / 0.8 mug/day = 125 mug/day

T3: ~ 7 / 0.95 mug/day ~ 7.5 mug/day

Higher/lower body weight and higher/lower than "normal" physical activity should increase/decrease these numbers.

[diogenes Remembering in reply to qvacuum]

One should remember that these calculations are only an average response. The individual's thyroid and T4-conversion-in -the-body T3 production will vary considerably from person to person. As will the calculated average of 20% of the T3 coming from the thyroid direct. In all these studies and calculations we forget the individual and only deal with the category - a basic flaw in medical thinking.

[tattybogle in reply to qvacuum]

typically, there seems agreement on the production rates for a healthy human

Is it agreement though ? , or just unquestioning repetition /reference in one paper after another of the 80%/20%. figures, with each paper referencing the last as more evidence.

It looks like a lot of the 'agreement' is simple repetition of the same research, (80%T4/20%T3 seems to come from work by Pilo et al. who looked at a whole 14 people and picked the one in the middle to serve as 'normal ' despite the other 13 having hugely differing levels.)

[Angel_of_the_North in reply to qvacuum]

Ah, but doesn't that "agreement" result from averaging the differing results from Pilo's study, which actually shows that people - and their ratios of T4 to T3 are very different. thyroidpatients.ca/2019/06/... and thyroidpatients.ca/2019/06/... for starters

[ak_83 in reply to qvacuum]

Thanks for being the only person to actually give me some solid numbers.

I know they may be flawed and that we're all different and that supplementing is different again. But I just wanted to understand what the healthy levels might look like, which your answer has done splendidly!

[helvella Administrator Thyroid UK]

The question itself is missing an important element.

Even if you knew how much new T4 and T3 is released by a healthy thyroid each day, even those figures for your thyroid when it was healthy, you are missing a vital element. The amount of T4 converted to T3 by the thyroid.

And that is without even starting on the questions as to how much T4 is converted to T3 and then released back into the bloodstream around the body.

You might well be remembering figures such as 100:20 - but that is quite likely because so many numbers have been quoted over the years. Sometimes pure guesswork. Sometimes with some scientific basis.

You are also missing the issue of the difference between the amounts in the tablets, and the amounts that reach your bloodstream. And whether you are referring to the amounts by weight or molar quantities. (Many formal documents fail on these points.)

And 100 micrograms of T4 doesn't convert to 100 micrograms of T3. Closer to 84 micrograms if perfectly converted. That represents the loss of an iodine atom from each molecule of T4.

[helvella Administrator Thyroid UK in reply to helvella]

I'll add to that, I am becoming increasingly convinced that dosage patterns are also critical.

A healthy thyroid will release tiny amounts of T4 and T3 - and convert some T4 to T3 throughout the 24 hours of each day.

Any currently feasible dosing regime drops a pretty substantial amount of T4 and/or T3 into the system once, twice, three or four times a day. (There might be the odd person who divides their doses up even more. And some research might have gone further.)

If your body fairly suddenly has a rise in thyroid hormone (T4, T3 or both), it will react. Maybe it will increase rate of sulphation and glucoronidation - followed by excretion? Maybe it will clampdown on release/conversion by any remaining thyroid capacity? That is, the simple fact of taking a dose changes the system. A body which might work with 100 units of thyroid hormone a day when healthy, will inevitably need more when that is exogenous, whether that is 101 or 150!

(This is not arguing for or against any dosage pattern. One might work better for one individual than another.)