How much T3,t4 body still produce when on NDT? - Thyroid UK

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How much T3,t4 body still produce when on NDT?

confused85 profile image
14 Replies

I am confused about NDT dosing. When I was on 1 grain of Thyroid-s (which is 38mcg T4 and 9mcg T3), my TSH levels went down to 0.01 and my T3 was 5.4 (reference range. 2.6-5.7)

I read that normal thyroid gland produces on average of 100 mcg T4 and 6 mcg T3 daily, although it secretes closer to 10 mcg T3 daily, because some T4 to T3 conversion occurs in the thyroid gland before release.

So this means even if TSH is only 0.01 which is almost undetectable, thyroid is still 50+% active. Is my conclusion correct or am I missing anything?

14 Replies
floraldaisy profile image

Mine was 0.1 and the dr said I was normal!!!!

Clutter profile image


TSH has nothing to do with how active or inactive the throid gland is. TSH responds to circulating levels of FT4 and FT3 and it doesn't matter whether it is produced from your own thyroid gland or NDT. I have no thyroid gland and my TSH is <0.01 on thyroid replacement but it was 107 when I was off thyroid meds for 4 weeks.

confused85 profile image
confused85 in reply to Clutter

I wouldn't agree with you. If my TSH when off any medicine is 4 and it is 0.01 when on medicine, this has some relation how thyroid is active. I agree it is not reliable sign as doctors say, but still you can not say it has nothing to do with how active is. Doctors are going from one extreme saying TSH is strong sign, but you are going to another extreme saying TSH doesn't tell you anything, the true is probably between.

Clutter profile image
Clutter in reply to confused85


Yet my TSH can vary between <0.01 to 107 when there is no thyroid present so definitely no thyroid activity whatsoever.

I didn't say TSH tells you nothing. A low TSH tells me my dose is sufficient to prevent TSH stimulating any remnant thyroid cells left after surgery. A high TSH will tell everyone they are under medicated.

shaws profile image

I wouldn't bother too much about NDT dosing. It is the very original replacement for hypothyroidism since 1892 and used successfully ever since. The way then was to take sufficient NDT until there was relief of all clinical symptoms. No blood tests. It was the only product until the introduction in late 50's/60's of levothyroxine along with the blood tests when there was the push to get rid of NDT by spurious methods.

The 'modern' method of diagnosing by blood tests alone doesn't bode well for many members when they have a myriad of symptoms. Neither does adjusting doses up/down to try to keep the TSH somewhere in the range.

The blood tests used today are for the use of levothyroxine alone. So if we are taking other than levo, we will have different levels and the most important question is 'how do we feel' not blood tests which should only be a guide..

Also, we don't now have 'normal' thyroid gland producing hormones when necessary but a substitute.

C70rol profile image
C70rol in reply to shaws

I would like to add to Shaws comments regarding dosing on NDT, that my own GP, who prescribes my Armour isn't bothered about blood test results. He has been prescribing NDT since before the synthetic drugs were made( the 60's).

He goes by the symptoms. And only tests at certain times of the year or when asked by me. When I quizzed him about "going a bit over range ", if I increase my meds recently, his comment was " the range is an average figure ,if my patients are comfortable and optimal slightly over the lab range, then that is where the patient needs be."

I hope that helps.

shaws profile image
shawsAdministrator in reply to C70rol

Oh - if only doctors were all like him. We must not publish his name as we don't want him ppearing before the BTA like Dr Skinner and Dr Peatfield to name but a few. There's been many more doctors who were persecuted and lost licences..

We definitely need more doctors like him to treat us, the patient, and not the test results.

DellFinium profile image
DellFinium in reply to shaws

My venerable US armour-prescribing doctor was the same...the GP would freak out at a the very low TSH (mind you, I always tested within a couple of hours of dosing) but consultant would reply that I was right where he wanted me to be. So, now I'm flying solo in UK, do I need to bother testing myself? I self-tested a year ago (before commencing self-dosing) and my numbers were identical to those on which he'd based diagnosis.

shaws profile image
shawsAdministrator in reply to DellFinium

You could always get a yearly blood test for everything i.e. also including vits/minerals. I self-medicate myself due to the fact that the T3 I was prescribed began to give me unpleasant symptoms. The following link may be helpful.

Dr John Lowe was also an Adviser to before his accidental death.

DellFinium profile image
DellFinium in reply to shaws

That looks like a really informative read - thank so much, shaws :-)

rjb112 profile image
rjb112 in reply to shaws

Very interesting post. Thanks.

floraldaisy profile image

Totally agree!!

startagaingirl profile image

Hi- I don't believe there is an easily calculated direct equivalent as the t3 in NDT is not the only factor. Don't forget that the t4 in NDT is also converted to t3 in the liver and other cells, with varying percentages from person to person and also dependent on an individuals level of nutrients. So there are a lot of factors in this for any individual, interesting though it might be to know what function is left! xx

Glynisrose profile image

TSH can become irrelevant when at low levels.

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