Optimal Percentage of t4 and t3 through the range

[redhead41]

What is the Optimal percentage of t4 and t3 through the range? Thanks

[GlowCoach Administrator]

That would depend if you're on Levo alone or Levo+T3 or NDT even. Often its also individual.

For Levo alone FT4 often needs to be in the upper quarter of range and FT3 around 70%.

For Levo+ T3 both FT4 & FT3 need to eb around 70% of range.

NDT is quite individual.

[greygoose]

Optimal is not a number, it's how you feel. There is no magic number to aim for, you just keep slowly increasing until you feel well.

When on T4+T3, there is no place where the numbers should be because the amount of T4 a person needs if very individual. Some people need a very high FT4, even when T3 is good. Others are happier with quite low FT4 - some, like me, don't want any at all!

You need to find what you need as an individual, but trail and error. Which is one of the reasons we start low and build up slowly. If you set your goals on any particular number, there's a strong risk you'll be disappointed.

[jimh111]

For a large group of patients with primary hypothyroidism their TSH, fT3 and fT4 on combination therapy would reflect the distribution of TSH, fT3 and fT4 in the healthy population. This may be a useful initial target for starting therapy but their will be variations as there is in the healthy population.Hypothyroidism can have other causes sich as endocrine disruption or pituitary problems that will require different doses.

I'm strongly opposed to the suggestion of targeting e.g. 70% of the reference intervals, it is more than the general population and will lead to increased mortality. Some people may need more but it's not a safe target for average therapy.

[redhead41 in reply to jimh111]

Thank you

[tattybogle in reply to jimh111]

suggestions of ' 70% / top quarter of range' make me nervous too.

People without thyroid problems have a wide variety of individual T4/T3 levels.

Some have T4 /T3 sitting in top 1/3rd of the range . but others have T4/T3 sitting in bottom 1/3rd of range .

Some have T4 sitting slightly higher than T3 , but others have T3 sitting slightly higher than T4.

So i find it difficult to believe that once taking thyroid hormone replacement all these individuals suddenly homogenise into needing top end for both . It's not logical.

i'm not suggesting people should aim for the same levels they had with a healthy thyroid ( even if they knew what those were , and most of us don't), because obviously thyroid dysfunction/ and taking thyroid hormones, changes multiple things.

But i do think it's likely that optimal levels for some people taking thyroid hormones could be significantly below 70% .

The example below is only 10 healthy individuals , so it's not proof of anything, but i hope it illustrates the point of how much healthy individuals vary in their needs :

thyroidpatients.ca/2019/09/...

,

[Tina_Maria in reply to tattybogle]

It is an interesting diagram and shows the variation in healthy people. The problem is that a normal thyroid can very easily adapt to different conditions throughout the day, for example, increase T3 when being more active. The TSH also changes throughout the day due to the natural circadian rhythm. So if this is finely balanced, I do believe that some people can get by with low levels of hormones, as their thyroid can easily ramp things up when specifically needed.

In thyroid disease, patients cannot easily adapt to different situations, as the thyroid cannot produce these hormones and we have to rely on external supplies. In the case of levothyroxine, yes it is a storage hormone with a half life of 7 days, but we notice a peak plasma concentration around 3h, after which levels decline again. So all the daily needs have to be covered by that once a day intake of levothyroxine (and in some cases also supplemented with T3). And as all requirements have to come from this external supply, is it not plausible that some patients might need a slightly higher level as perhaps a person without the disease, so there is a certain 'store' of hormones, which can satisfy all the requirements throughout the day.

Of course, we should always aim to take the lowest dose which is effective in alleviating our symptoms. However, I think it is not that helpful comparing our intake (which is artificial) to an adaptable production of thyroid hormones. And perhaps this is why patients on medication might need to run a higher level.

For example, type 1 diabetics relying on insulin use far less insulin when they are on a closed loop system (artificial pancreas, where continuous glucose measurements are taken and insulin is given as required). If we had an 'artificial thyroid' with corresponding (functioning!) TSH feedback, we would be able to fine-tune our thyroid hormone requirements much much better and we would quite likely need less hormones than patients seem to require at present.

[jimh111 in reply to Tina_Maria]

Good point, we lose the adaptablity and will need a slightly higher dose. We store around 10 days worth of levothyroxine so any peak after taking a tablet is small. Also, the diurnal fluctuation in T3 levels is small, around 6%. Taking T3 does give a large variation in fT3 but Celi has shown that thrice daily dosing will overcome this as measured in fluctuations in TSH pmc.ncbi.nlm.nih.gov/articl... . Thyroid hormone receptors are saturated with T3 for several hours before they activate, this in part explains why short term variations in fT3 are not reflected in tissues.

[tattybogle in reply to Tina_Maria]

all good points , especially the adaptability of a functioning thyroid .

the point i was attempting to make is not that we should use these healthy people's levels as a guide to what levels we need now ( we all agree that lack of functioning thyroid and taking a fixed daily dose of thyroid hormones will change multiple things )

but rather that it is illogical to expect that everyone would need eg 70% once on levo.

several of those people have fT4 consistently around 25%, so even if they needed more once on levo, that might be eg. 50% .

[Tina_Maria in reply to tattybogle]

Completely agree, the hormone requirements of healthy people is very individual, as are the requirements of people with thyroid disease (even if they might have a slightly higher need than before their disease).

I'd be happy if the medical profession would at least accept that we all have different requirements and that one size does not fit all! They all talk about personalised medicine these days ... only no one is practicing it! 🙄🫣

[Mednews4 in reply to jimh111]

question - are you saying that 70% range in both t4 and T3 has increased mortality or just one of them.

[jimh111 in reply to Mednews4]

Both. T3 is active at thyroid hormone receptors and so affects metabolism. T4 activatese the integrin alpha-v-beta-3 receptors on the cell membrane and fT4 in the upper part of its reference interval is associated with cardiac and cancer mortality. LT4 monotherapy needs fT4 in the upper part of the reference interval and there is evidence of increased mortality. For this reason I am no longer in favour of LT4 monotherapy even if the patient is doing well on it. In healthy people fT3 and fT4 vary but it's unusual to see both near the upper 70% mark. These are relative effects so we shouldn't try to be too precise.

[Buddy195 Administrator]

As others have advised, ‘optimal’ is individual. Personally, I feel ‘jittery’/ anxious with FT4 above 70%, but am fine with FT3 higher in the range. We all have our different ‘sweet spots’ where we feel most well. I’m a fan of adjusting thyroid medication super slowly (eg adjusting by 12.5mcg Levo) so I don’t miss my ‘optimal’

[Transalp]

I use an RMR test as another way of looking at it. When my FT3/FT4 were in range my first RMR test had me at 68% of what would be expected - around 700 calories a day difference - and yes I was fat and lethargic.

After increasing my medication, but still in range, my last RMR test had me at 96% of expected. I do feel more active.

[L154C0]

I’m sure this has been answered elsewhere, but how do you work out where your t3/t4 is in range?

[helvella Administrator in reply to L154C0]

L154C0,

This pinned post:

Thyroid Test Results Calculators

healthunlocked.com/thyroidu...

[L154C0 in reply to helvella]

how does this translate as ‘through the range’? Sorry, I’m brain foggy AND blonde.

Latest TFTs

[helvella Administrator in reply to L154C0]

In the TSH range you have typed LETTER "Oh" - not zero!

FT4 is 6.9%

FT3 is 47.8%

And the little green line gives you a visual indication.

[L154C0 in reply to helvella]

oh indeed 🤦🏼‍♀️

[redhead41]

Thank you everyone for your replies

[Bearo]

I’m glad you asked the question, redhead41, as the discussion has been well worth reading.

[Mednews4]

I'm a bit confused. Just had my results back and I truly am not sure if these are optimal or not. I feel okay but have weight gain and i also am concerned about the heart mortality issues discussed above.

[redhead41 in reply to Mednews4]

Can you please post your results with the ranges

[Mednews4 in reply to redhead41]

FT4: 1.3 pmol/l (Range 0.8 - 1.7) 55.56%

FT3: 2.9 pmol/l (Range 2 - 4.4) 37.50%

[redhead41]

T3 is too low - most people would do better with both t4 and t3 nearer 70% thru the range