TSH/T4/T3 & Antibodies for Diagnosis?

[Jeffina]

Why do some regions only test the TSH level?

Other regions test TSH with T4 and occassionally some also test the T3 too but that's rare and usually the patient has to request it, which relies on the patient knowing more than the doctor.

Surely you need all 4 looked at together EVERY time for a correct diagnosis and at the very least TSH and T4 (but ideally with T3) with every further test for good management along with signs and symptoms?

I know some PCTs/labs state cost as the deciding factor but surely there's little point in testing the TSH only - isn't that a waste of money as the patient needs to keep returning for more tests to reach a diagnosis (if they ever do).

I personally had around 5 sets of full blood counts and several TFTs until I finally researched thyroid disease for myself and realised the doctor should be testing my antibodies as my mum has thyroid disease. I actually had to inform my GP what to write on the blood form as they had no idea. Had my antibodies been tested the first time I went to the GP with my obvious hypothyroid symptoms the NHS would have saved a lot of time and money over unnecessary blood tests.

This was in 2009, not that long ago - clearly the message does not filter down very well to GPs about what tests and treatment should be given to thyroid patients.

Shouldn't antibodies be tested with any suspected thyroid problem as a matter of course?

[Professor John Lazarus]

In USA they generally only rely on TSH even in the very best clinics
I agree that if there is a family history of thyroid disease or autoimmune disease thyroid antibodies should be measured.
Measurement of T3 is not helpful in the diagnosuis of hypothyroidism
The British Thyroid Foundation will be discussing the best way to provide more thyroid eductaion to the medical profession

[Jeffina]

Thanks for the reply. I'm not sure if you misunderstood me but by other regions I meant within the UK - others counties, rather than other countries.

In my experience swapping notes with many other thyroid patients around the world I would not say it was strictly true that they only go by the TSH in the US. In fact most thyroid patients in the UK would say we are trailing way behind the US in how thyroid patients are treated and managed and as you have noted yourself TSH alone is not adequate for diagnosis or management.

Can I ask you to explain futher why measuring the T3 is not useful in diagnosing hypothyrodism? Would you consider it useful in the management of the disorder?

I thought that T3 was the 'end result' as such, that it is the actual useful part, after one iodine atom is lost from T4, which is mostly a storage hormone, T3 is the part of the hormone that does the work?

I am extremely pleased to hear that the BTF is looking to educate the medical profession further on thyroid disease because there needs to be much clearer guidelines that mean that GPs and endocrinologists alike do not end up so confused they are contradicting each other or worse still so scared ot trialling patients on thyroxine or liothyronine that they prefer to put them on antidepressants and leave them to 'get on with it' without a diagnosis.

[Dr David Kerbel]

Thyroid antibodies should always be done initially in my opinion when diagnosing hypothyroidism as they help confirm Hashimoto's thyroiditis which is auto-immune. A v small percentage of hypothyroidism is not auto-immune.
As a diagnosis of hypothyroidism will mean you need lif-long treatment I feel it is worth doing autoantibodies initially.
Thyroid autoantibodies are also useful in clarifying diagnosis & making decisions about whether to treat subclinical hypothyroidism (when TSH between 5 and 10).

My lab in Leicester only does TSH levels for hypothyroid management.
Actually this makes sense as biochemical management revolves around TSH & getting it below 2 but above 0.3.
There are complex negative feedback loops to hypothalamus, pituitary, and thyroid itself which mean that T4 levels are irrelevant & confusing in this situation. I realise it appears confusing that we arent measuring T4 & T3 themselves but they dont generally help clinically.
TSH actually gives a better idea (thermometer if you like) of bodies requirements.
When one does get TSH into therapeutic range, invariably T4 & T3 will follow.
(Converse does not apply! Normal T3 & T4 levels do not necessarilly mean hypothyroidism is properly treated).

Our lab will do T4 & T3 for hyperthyroism and when specificially requested (usually by endocrinilogists) although they have done it for me - a GP, when I specifically justify request.

My beef as a GP with an interest in this area & trying to spread good practice to colleagues, is that the labs (can only really say that my lab in Leicester) do not distinguish on their reports between screening levels of TSH - 0.3 to 5 and treatment target levels of 0.3 to 2. There are unfortunately a number of my colleagues (GPs) who arent aware of the difference in ranges. Thus patients may see their GP and be told their TSH is normal when it is 4 (within normal screening range) when actually they need their levothyroxine (T4) increasing as the TSH isnt suppressed sufficiently to under 2.
I have struggled to get endocrinologists and chem paths to agree on target ranges I have quoted.

[Jeffina]

Dr Kerbel, thank you for the reply.

I wish more GPs shared your view of testing thyroid antibodies - it seems madness that it isn't standard to include this test in the initial blood tests for suspicion of thyroid disease. I honestly don't think that most doctors know of the connection between antibodies and how they can have an effect on the blood test levels.

My own GP did not even know what to write on the blood form when I first discussed it with him - I think this shows what a complete lack of understanding there is about it.

Can I ask you, if you are faced with a patient that has a history of thyroid disease in the family, clearly looks hypothyroid with classic (or even non-classic) signs and symptoms and their antibody test came back as normal would you still trial treatment? And by 'normal' I mean some circulation of antibodies but still within the range, say 12 in a range of 0.0-34.0?

I do have to disagree with your point about the TSH though. I know that my T4 varies wildly from the low end of the range (and below) to the top end of the range when my TSH is anywhere between 0.3-2. In other words the TSH test alone is not enough for patients or doctors to manage their symptoms with. T4 and T3 readings combined are much more accurate and going by the advice of Dr Toft we should all be aiming for a Free T4 in the upper end of the range.

If my TSH is between 1-2 my T4 is usually between 11-13 in a range of 12-22 so as you can see it's low or below range and I am extremely symptomatic with that kind of reading. I agree that 'normal' readings of T4 & T3 do not mean that hypothyroidism is properly treated - it is usually only when these levels are carefully monitored and raised up to the top quarter of the range that symptoms are eliminated.

Surely it should follow that if we are taking synthetic thyroid hormone because our own thyroid gland is not working correctly then we should be on a level that brings the TSH down very low as the signal from the pituitary gland isn't needed any longer, we are in effect over-riding the automatic response by providing T4 in a daily dose ourselves. Anything over 1 would indicate that the body needs more as the TSH signal is still being sent?

And where do you stand on patients that don't get along with T4 only therapy? Surely then the T3 test is a vaild one to check their are naturally converting T4 into T3? Problems in this area are more common than a lot of doctors believe.