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Thyroid UK
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Low TSH Blood Test Results following changing to Armour Thyroid

Hi Guys,

I was taking 100mcg levothyroxine until 20th January 2017. I managed to convince my Doctor to trial Armour Thyroid with me and I am currently taking two grains of armour thyroid, once in the morning an hour before food and one in the late afternoon/ evening time.

My health has been just fine, with no known reactions to the Armour Thyroid medication other than a rash on my foot at the beginning which I put down to an allergy to the new meds.. I feel just fine. My weight has even come down which is something that is important to me. I've been able to see more results of my exercise routine. I feel absolutely fine.

I ordered a Blue Horizon Blood test kit which cost almost £200 and had bloods taken on 22nd March 2017. I went in to the BMI Priory Hospital on an empty stomach, having not taken a grain of Armour Thyroid for at least 12 hours. The blood was taken around 11:50AM

I have reviewed my blood test results this morning and I am now posting them now.

Vitamin B12- 561 ( range 197-771)

Serum Folate: 7.8 ( range 3.9- 20)

Ferritin: 132 ( range 30-400)

c reactive protein: 3 ( less than 5 is normal )

Key results:


TSH:0.01 ( RANGE 0.27-4.2) ( pretty low- should I be worried?)

FREE T4: 13.8 ( range 12-22)

FREE T3: 5.7( RANGE 3.1-6.8)

vitamin D : 43( 50- 200) again quite low

Thyroid antibodies:

thyroglobulin antibody: 11 ( 0-115 range)

Thyroid Perioxidase Antibodies 16.7 ( 0-34 RANGE)

Reverse T3 : 18 ( RANGE 10-24)

So from these results, the two main things that stand out are the fact that my TSH is quite low and I have low vitamin D levels.

Armour Thyroid I have read can give these kinds of issues regarding TSH. I have also read TSH is a poor marker for judging adequate Thyroid Hormone Replacement therapy.

I feel absolutely fine health wise.

What are your views on these results? Any advice would be much appreciated. Should I worry about these results and what do you advise I do?

Many Thanks,

Jose x

17 Replies

If you feel fine with all symptoms relieved you are on the proper dose.

Before the blood tests and levothyroxine were introduced around the early 60's, only NDT was available and was prescribe due to our symptoms only on a trial basis and if patient improved they continued.

Also because NDT contains all of the hormones our healthy gland would have produced, T4, T3, T2, T1 and calcitonin the blood tests for levothyroxine cannot possibly be thought to be equal to being on NDT.

Levothyroxine is T4 and is inactive. It's job has to convert to T3 whereas NDT has T4 and T3, so TSH will also be lower and there have been quite a few articles about the 'Tyranny of the TSH' which keeps patient unwell as many doctors believe 'anywhere' in the range is satisfactory when it should be 1 or lower and some need it to be suppressed.


2gr of NDT is equal to around 200mcg of levothyroxine and one Dr, now deceased, said that the usual doses of NDT were around 200 to 400mcg and that nowadays we were given too low a dose of thyroid hormones (levo) for us to recover our health.


NDT will suppress your TSH. Nothing to be overly concerned about unless you are high risk for heart disease or osteoporosis

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You left a long time between your last dose of NDT and taking the blood so you need to upscale your fT3 figure, perhaps to around 8.0. This will explain the suppressed TSH. You are on about twice the dose of hormone now (NDT manufacturers usually say 1 grain is equivalent to 100 mcg levothyroxine).

There's no reason NDT should suppress the TSH unless you are on a dose that is high enough to suppress the TSH - you may need this dose.

So, your TSH is very low and this presents a risk of atrial fibrillation and bone loss. On the other hand if you are very hypothyroid on a dose that does not suppress the TSH then you don't have much choice. Chances are if you can't recover on L-T4 or L-T4 plus a small amount of T3 medication then you have some complex form of hypothyroidism and may need to suppress the TSH. In this case there is a small risk of AF and bone loss. In which case taking exercise will reduce both risks. Doctors (and some patients) seem to assume there is a zero risk option that gets you well.

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The Rotterdam study showed no correlation between low TSH and bone loss, BTW (or so little as to be statistically insignificant). Although it has been shown to be a risk for hyper patients with over range FT4 and FT3.


There are a number of studies showing the effects of low TSH on bone mineral density. It's some time since I read the Rotterdam Study but the abstract ncbi.nlm.nih.gov/pubmed/178... clearly states "serum TSH shows a positive trend with BMD in human subjects".

However, if suppressing the TSH makes the patient well and enables them to take exercise they will be able to mitigate these effects and have a better life.



The Rotterdam Study found no association between TSH and atrial fibrillation and the meta-analysis of patients with TSH <0.1 found one extra hip fracture in 1,000-patient-years.




Referring to 'The Rotterdam Study' is prone to confusion as there are a number of papers arising from this study. I haven't studied the one you quote but a quick glance shows it analyses risk of AF in subjects with normal TSH and fT4. TSH is quoted as 1.91 (1.29 - 2.77), so 95% of the cohort were very normal. I would fully agree that a TSH within the reference interval will not lead to a risk of AF, whether TSH is near the top or bottom of the interval. I'm suprised at the link with fT4 although at initial glance it is not clear whether subjects with the higher fT4 have a naturally higher fT4 or are on levothyroxine.

I will get your second reference from the BL sometime. The title states there is an increased risk of fractures. I don't see a reference to ONE extra fracture, do you have a full copy of the paper. In any event I don't like meta-analyses, they tend to aggregate unlike data and fail to analyse the studies. Also bear in mind that although a suppressed TSH lowers BMD if it enables the patient to take exercise they would not normally be able to do this might mitigate any risk of bone fractures.



I don't have the full paper. Diogenes assessed the risk to be one extra fracture from the data. I didn't bookmark the post unfortunately.



sorry your wrong 1 grain of NDT will only relace about 60 mcg of levo

my husband was on 350mcg of levo or 120mcg of straight t3

but he is fit and well at age 74 on 5 grains of NDT

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The manufacturers of NDT tell us 1 grain is equivalent to 100 mcg L-T4, I'm taking their word for it. Unfortunately you can't just add up the T3, T4 contents as the medicines will have different pharmacokinetics. The best test we have is to compare the effect on TSH, as is done to determine the relative potency of L-T3 and L-T4. Your husband is on supra-physiological doses of thyroid hormone so it is difficult to compare equivalence because the deiodinase mechanisms that apply at normal hormone levels do not apply. I don't know of any study that compares the potency of NDT versus L-T4 so all we have to go by is what the manufacturers say, which may not be correct!


many many men are on 300 or 350mcg of levo

the Prof who diagnosed my husband had some people on 700 or 800mcg of levo

i think you will also find that after Original Graves and then surgury or RAI patients are only well when their freet4 and freet3 are way at the top or slightly over the top of the ranges



TSH is suppressed because of the amount of NDT you are taking but you aren't over medicated because FT4 and FT3 are within range. Because of the 12 hour gap between last dose and blood draw your FT3 will be higher than 5.7 but is probably still within range.

VitD is optimal around 100 nmol/L. I would supplement 5,000iu D3 daily and retest in July/August. Take VitD 4 hours away from NDT.



when on NDT or any T3 containing meds your TSH will always be liw or zero

its the perfectly natural response of the pituarity thyroid feedback system

its a basic biologic fact that satisfy the loop and body with adequate levels of thyroid hormones your TSH will be redundant

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Wish I understood all of this 🤔🤔🤔


Hi Guys,

Thanks for all your responses! I am a 28 year old man FYI and I am active, I workout in the gym and the football pitch 4-5 days per week. I did leave it about 12 hours between the last dose and the blood draw- I wasn't aware that this was a bad idea . So next time I get my fasting bloods done, should I leave a 24 hour gap?? I shall try and get in earlier!Please let me know.

Of course, I do not want to do any harm to myself. I feel great on this dose and much better than on t4 only meds. I can't explained how good it felt losing almost a stone over the past three- four months on this dose. I actually cried because I was giving up hope of getting my life back..

When should I take my next blood test?

I need to show my Dr these results. I am kind of apprehensive of what to say to her- hope she doesn't reduce the dose as I feel well- what is the best way of tackling this problem?

Many thanks all,




This sounds good. From a blood test point of view you should leave about five or six hours after your last dose since you take your NDT about 12 hours apart. This will give you a good indication of your average hormone levels. You should not have the blood taken within two hours of taking the NDT as it can give false results.

The risks of a suppressed TSH are real but they are small, they are higher in the elderly. So as a 28 year old I wouldn't worry. It's true that you will run into higher risks in another 30 or 40 years but we hope that there will be a much better understanding of hypothyroidism by then. Your exercise is the perfect answer to any risk of AF or bone loss due to a suppressed TSH. You have to bear in mind that at your age the risks are very small and in any event remaining clinically hypothyroid carries a greater risk of congestive heart disease from elevated cholesterol levels and a sedentary life style. It's also a question of having a life as opposed to existing longer.

As regards what you should say to your doctor, I would suggest what I did (I take liothyronine). Tell your doctor how you were before the switch to NDT and describe the impact on your day to day life. Also mention the exercise you do and how NDT enables you to continue doing it. I'd also offer to check your pulse once a month as a way of monitoring your heart. You can buy a machine that measures your heart and blood pressure, they are quite cheap. Or pehaps you already have some kind of exercise monitor?

Although I went into a lot of technical detail the point I'm making is that a suppressed TSH carries a small risk, mainly in the elderly, but there are also risks from remaining clinically hypothyroid. I don't want to give the impression that a suppressed TSH is risk free, just in case patients completely ignore it. Simply stay on the minimum dose that resolves your symptoms and perhaps try dropping it a tiny bit every couple of months just to see if you still need the full dose.

You could do another blood test in three to six months, just TSH, fT3, fT4. Reverse T3 is a waste of money, especially you are now on Armour. Your antibodies are low, there's no point in another assay. Although your vit D is low I'd suggest you just supplement with vit D3 during the winter and play some football in the summer. I wouldn't bother testing vit D again, winter supplementation and outdoor activity will sort it. If your doctor really presses you could try a combination of levothyroxine and Armour. This might not work but there's no harm in giving it a try. In the longer term I'd do a blood test about once a year assuming you are not getting any signs or symptoms of hyper or hypo thyroidism.


Low TSH can be irrelevent when taking any form of thyroxine.

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