Thyroid UK

How TSH Ranges Are Determined

I just went for an aldosterone test this morning. I had to go to the pathology lab at the local hospital, so I asked the girl doing the test if she knew how the TSH ranges were decided. She didn't know exactly how the ranges were worked out, but she said it was done using tests that were sent in "from patients who haven't been diagnosed with clinical hypothyroidism".

For me that puts the nail in the coffin of TSH ranges - not to mention T4 and T3 ranges. There are so many holes in that way of working out the ranges that the bucket has sunk.

I'd like to define, in medical and scientific terms, why that method is meaningless. These are the reasons that occur to me off the top of my head as I'm typing. If you have others to add, please do.

1) Many of those patients will have been exhibiting symptoms of hypothyroidism, which is why the blood test was done in the first place

2) It is a self perpetuating circle, as patients cannot be diagnosed with "clinical hypothyroidism" if they are within the range previously set. So the range cannot change.

3) Even those patients who aren't exhibiting signs of hypo may have compromised tests if they are suffering from other conditions or taking medication

To set a true range, tests would need to be taken from healthy volunteers who, on questioning and examination, show no signs of hypothyroidism.

Comments please.

4 Replies

Exactly - but will that ever happen? You honestly have to wonder who thinks these things up and don't even get me started on how wide the ranges are. My pet complaint is that it is almost impossible not to come somewhere 'within the range' by the time you are not in range you are probably so ovbiously ill that they don't need to do tests to find out anyway.

Liz :-)

1 like

Anything for an easy life- especially if you get in the first strike, like the Drug companies have managed to do, with an all too compliant medical establishment.

Happy with guidelines [that aren't really] -and unable to take on more due to 'overuse' of the NHS. [£1Bn for diabetes for a start]

Sounds about right- but then, I'm a old cynic...

The Scottish petition should shake things up- but who knows what wriggling [&/or delay] will ensue on the other side?


Life was so easy before the thyroid gland blood tests were introduced - patients diagnosed according to clinical symptoms. Given a trial of thyroid hormones (natural dessicated) and dosed till symptoms went. Obviously if there symptoms didn't it must have been due to something else. I have read that a trial of thyroxine is harmless.

Nowadays, I would like to know how much money is spent on TSH blood tests, and other thyroid gland blood tests; how much is spent on other medications to treat clinical symptoms due to being kept 'within the TSH range' etc. etc.

Dr Lowe stated that we can get other more serious diseases such as heart, cancer or diabetes - excerpt

Four studies I discuss in the critique showed that T4-replacement and T4/T3-replacement leave many hypothyroid patients suffering from hypothyroid symptoms. A fifth study I cite suggests that some patients on T4-replacement develop potentially fatal diseases. The patients also regularly used drugs to control their symptoms of hypothyroidism and the other associated diseases. Other studies I cite showed that patients taking higher-than-replacement doses of thyroid hormone have superior treatment results. “TSH is Not the Answer,” report - see below.


A number of years ago the typical reference ranges for TSH were tightened markedly after applying stricter criteria on those whose samples were used to define it. This excluded anyone with any known history of thyroid issues and those with either TPO or TG antibodies. If done properly, and I think it has been in at least some labs, it also excludes those being tested because of suspicion that they have a thyroid disorder. That is, the reference range should not be established by looking at test results of those who might have an issue but of those who, to the best ability of the lab to determine, are unequivocally not ill at all and most certainly not with any thyroid or thyroid related disorder.

Numerically the tops of ranges did get lowered across much of the USA and the UK. There was little change at the bottom of the ranges.

It was also especially important to exclude those who have, or might have, antibodies to TSH as the macro-TSH which occurs (where a TSH molecule is attached to a TSH antibody) is well known as a interfering factor in TSH tests. Some TSH tests have been modified to preclude any interference from macro-TSH.



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