Routine Hypothyroidism Tests – Understanding Why They Are So Inadequate
The present generation of hypothyroidism tests are fine if you already have a full-blown case of hypothyroidism.
However, for the millions of people suffering from mild thyroid failure, such tests are utterly inadequate.
So, how can we ensure that even the milder forms of hypothyroidism, often called underactive thyroid, or subclinical hypothyroidism are equally visible upon thyroid testing?
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Hypothyroidism Tests Are Only As Useful As Their Interpretation
A major basis to this discrepancy in hypothyroid testing is the manner in which such medical tests are interpreted.
For instance, one hypothyroidism test is the TSH blood test (thyroid stimulating hormone). At present, the range of 0.5 to 4.5/5.5 is based on what's considered a normal, 'standard reference range' as determined by experts in the USA, as of February 2010.
To make things even more complicated, this upper figure can vary from lab to lab, making the concept of 'standardized medicine' - as touted by most doctors – in itself rather dubious.
First, Let's Explore How Thyroid Function Tests Are Done
To get a real sense of thyroid gland function, let's go a bit deeper into how the present hypothyroidism blood test is done, and then broaden the discussion to include ways of being able to pick up this level of otherwise 'invisible' thyroid dysfunction.
At present, TSH (thyroid stimulating hormone) is usually the first of the blood tests ordered by medicine, to ascertain whether thyroid function is at an adequate level or not. Another blood test would be a FT4 (free T4) and/or a FT3 (free T3) test.
Other blood tests for hypothyroidism which should be thought of include those testing for thyroid antibodies, consistently found in various forms of autoimmune thyroid disease, such as autoimmune thyroiditis, (also called Hashimoto disease).
These comprise the thyroid peroxidase antibodies (the most sensitive ones for Hashimotos), anti-thyroglobulin antibodies, and anti-microsomal antibodies.
Thyroid Deficiency Can Be Due To Inactivated Thyroid Hormone
The 'F' in front of the T4 and T3 indicate that such blood analyses are specifically looking for the amounts of freely available T4 and T3. This is an important distinction to make – and test for - since the thyroid gland, upon manufacturing these two hormones, 'wraps' the bulk of them in a storage protein called 'thyroglobulin'.
Most of the T4 and T3 circulating around the body, via the blood, is bound to and thus inactivated by a variety of carrier proteins – much like a truck 'inactivates' its load as it transport that load from one point to another.
However, when T4 and T3 are bound up in this manner, it makes them inactive: hence the importance of only measuring the amount of unbound, and therefore potentially fully active form of the hormones.
But What is a 'Normal' Hypothyroidism Test Result?
So, how is a 'normal' thyroid function test range determined? Well, here we encounter some interesting anomalies!
Firstly, the way science and medicine determine an average, or 'normal' result is by combining the blood results of many thousands of people. These results can be plotted in a graphical manner to create what is called a 'normal distribution curve' or 'bell curve' – so called because of its bell-like shape, as shown below.
Diagram 1 - 'Normal Distribution Curve'
This curve therefore represents the range
of all readings taken within a sample, from the very lowest results to the highest, as obtained via thousands of blood results for any one particular health condition. In this case, these results would be associated with the hypothyroidism tests your doctor will have ordered.
Explaining The X And Y Axis Of This Graph
The Y-axis (vertical line) represents the number of people
obtaining a certain result. As one goes up
that Y-axis, so too does it represent an increasingly higher number of people obtaining a certain result in the study.
In turn, the X-axis (horizontal line) represents the actual test score
obtained by people for their hypothyroidism tests; in other words, the actual amount
of something found within the blood sample tested – in this case, levels of TSH, FT4 or FT3 hormone.
Again, starting at the extreme left-hand side of that X-axis, this represents the lowest scores or amounts found in that testing procedure.
In the middle of the X-axis, where the bell curve is at its peak, this represents the results achieved by the greatest number of people within a particular test.
And finally, at the extreme right-hand side of the X-axis, this again represents a small
number of people obtaining the highest
readings achieved in that study.
A Normal Distribution Curve Is a Powerful Visual Tool
Hence, a 'Normal Distribution Curve' is a useful mathematical 'tool' through which to get a quick, clear, visual understanding of which numerical result, found in a study group of people, was also attained by the majority
of that group.
By looking at the curve, it becomes easier to see that the test result obtained by the greatest number of people in the population sample is represented by the very peak of that curve.
This mathematical tool can also be used to give a quick and easy visual understanding of what is elected to be the 'normal' range of results. As can be seen from diagram 2, two lines have been drawn towards the ends of either side of the curve, where that curve starts to approach the bottom, horizontal line, or X-axis of the graph.
Diagram 2 - 'Normal Distribution Curve - Defining Normality'
Normality For Hypothyroidism Tests Is Ultimately Based On An Arbitrary Decision
The results for the hypothyroidism tests, found between these two arbitrary lines, are the findings, which – as decided by a professional medical panel, and based on the present
level of research – indicate the range of readings considered to represent a state of health.
To some extent, such demarcations of what is considered 'healthy' or 'unhealthy' – according to these distribution curves - are rather subjective. The 'healthy' range can change when new research brings a different understanding of what is 'normal' or not.
Hence, 'normal ranges' derived from test results can never be considered an eternal truth. They can only be considered the 'right result' based on our present
understanding of the science associated with a particular situation.
For example, this point is validated by how medicine has frequently changed the 'normal ranges' used in cholesterol and diabetic testing. Such modification now also needs to occur, especially within the TSH 'normal' range.
Recommendations By The National Academy Of Clinical Biochemistry – And Their Implications
This Academy did research, presented in their 'Laboratory Medicine Practice Guidelines for the Diagnosing and Monitoring of Thyroid Disease',
(ref.1) which recommended in late 2002 that the upper limit of normality for TSH be reduced to 2.5mIU/L, rather than the present 3.5 to 5.5 reading.
Such a significant shift was driven by research findings which showed that 95% of volunteers considered by thorough testing to be normally healthy, present with serum TSH levels between 0.4 and 2.5 mIU/L.
Shifting the 'goal-posts' in this way does have serious ramifications, because further research showed that if the upper normal range of TSH levels is kept at 5.0, then this results in about 5% of the population being diagnosed with 'valid' hypothyroidism.
However, if a lower reading of normality is accepted, this in turn results in about 20% of the population being recognized as suffering hypothyroidism – and this would be full-blown
hypothyroidism; not subclinical
What this subsequently means is that at present, and based on research and recommendations by major players in the Biochemistry Screening industry, at least 15% of those presently tested for hypothyroidism, are not being picked up – and therefore also not treated
'Normal' Results Are Derived from Ill People
And here's the rub. It needs to be clearly understood that at present most of these 'normal' ranges, as shown by the various distribution curves discussed above, are inevitably based on cumulative data from ill
Despite the research stated above, most labs do not
determine the 'normal ranges' for their blood results based on perfectly healthy people. In other words:
• Often, a population of ill people is used from which to extract what can be considered a 'normal' result – surely, a contradiction in terms?
• Although many different laboratories may pool their results for any particular health issue being tested, this doesn't change the fact that all
those readings are based on the blood tests of people who have precisely gone to their doctors... because they were feeling ill.
• These figures immediately create a bias in any interpretation deduced from such results, no matter how well the data has been collected and collated. So too with hypothyroidism tests.
Yet, medical, therapeutic decisions are all too often made – or not made! - upon such skewed 'normal ranges', which were recommended to be changed almost a decade ago.
This is a rather large elephant in a very small room – which is either ignored or not taken into consideration when such results are subsequently used to direct therapeutic decisions.
Diagnosing Earlier Stages of Hypothyroidism Would Also Allow For Earlier Treatment
Since hypothyroidism type 2, or subclinical hypothyroidism is relatively easy to treat (see: 'Hypothyroidism Treatment'), and because this level of hypothyroidism is also a pre-stage
to full-blown, classical hypothyroidism, a value of 2.0 – 2.5 as the upper limit for normality within hypothyroidism tests should be taken seriously, particularly if a patient presents with a range of hypothyroid-like symptoms.
The problem is that too often medicine still works in a reactive and retrospective manner – in other words, far too often doctors only respond therapeutically when patients present with full-blown
cases of their disease.
Those who present in the earlier phases of dysfunction are inevitably not diagnosed, because the narrow interpretation of various diagnostic results precludes the use of pro-active and preventative treatment strategies.
Instead, a more refined interpretation could validate such diagnostic results, while also acknowledging what a patient is saying about their condition
– rather than judging such patients as hypochondriacs, because present test interpretations erroneously indicate 'all is well'.
From a human-suffering level, as well as an economic perspective, surely it would better serve to be more preventatively orientated?
Present 'Normal' Ranges Can Still Be Used – Just Interpreted Differently
By the same token, this discussion doesn't mean we now stop using such potentially flawed 'normal ranges'; not in the slightest. It does, however, mean that we need to keep these above points of discussion in mind when we interpret – always a more subjective
process! – various blood-based diagnostic results.
It also means that we need to be more flexible in determining who may be ill and who not - by using more up-to-date interpretations of blood-based hypothyroidism tests, for example.
This is especially so when that patient sitting opposite us does come in with a recognizable range of symptoms, suggesting – for instance, some sort of thyroid disease – even if their hypothyroidism tests keep coming back as 'normal'.
For any doctors reading this discussion about anomalies associated with blood tests, who or what are they now going to give more credence to? Their patient... or a piece of paper from a laboratory? Ultimately, that's what it comes down to.
Just Scraping Into The Lower 'Normal' Range Doesn't Necessarily Mean 'Healthy'
One final point needs to be made at this stage in regard to how hypothyroidism tests, and other diagnostic procedures are interpreted. Going back to the 'normal distribution curve', and as touched on earlier, once science and medicine determine an arbitrary cutoff point at both ends of that curve, far too often they then consider all
readings within that entire range to be equally
To clarify this point, have a look at the above diagram 2 again, and you'll see that the area between the two cut-off points includes a rather large range of test results, from lower 'normal' to upper 'normal'.
Unfortunately, there are still many doctors who regard the entire
range of readings between lower and upper 'normal' as being essential the same
- i.e. indicating a 'healthy' or 'normal' state within the person tested. This is unrealistic, let alone unscientific!
What is being ignored is the fact that although one person may just have scraped in at the bottom
end of a 'normal range', such a reading does not indicate that
person to be necessarily equally healthy or functional to another person whose reading lies just inside the upper
range of readings.
Although both do indeed lie within the 'normal range', surely – even mathematically if not physiologically – these two end readings cannot
be considered under the same banner of 'normality'?
Readings At Either Extreme Ends Of The Curve Indicate Impending Dysfunction
Surely, this point of discussion would at least suggest that such a person – presenting in either extreme end of the 'normal distribution curve' - may in fact be on the brink of early
Does this not equally suggest therefore, that such a person may need to have pro-active treatment choices made, in order to minimize the possibility of deteriorating into a full-blown ill-health state?
Hence, any presenting symptoms they come in with need to be given even more
validity than if their reading were to come right in the middle of that curve.
'Thyroid Resistance' - Like 'Insulin Resistance' - Can Be A Major Driver Of Symptoms
Hence the key message from the above discussion is that for a whole range of reasons, the T4 levels found in hypothyroidism tests may appear to be 'normal' within this subclinical hypothyroidism scenario. More likely than not, via various feedback mechanism within the system, this in turn will cause the TSH blood test result to seem 'normal' too.
Hence, the term 'thyroid resistance' – in relation to this level of thyroid dysfunction – would therefore seem more than appropriate for highlighting that such dysfunction can be associated more with the peripheral
as opposed to solely a central
In other words, enough FT4 may exist within the blood, but it's the inability of such thyroid hormone to function effectively on a cellular level that then creates this reality of 'thyroid resistance'.
In turn, all these points beg the question of: 'what is the value of solely using TSH, T3 or T4 as one's diagnostic yard-stick for hypothyroidism, when this health issue goes far beyond simply a thyroid gland dysfunction or failure'
Some Concluding Thoughts
Is it perhaps becoming more clear why solely relying on just a TSH, T3 and T4 blood test result as the decisive indicators of a thyroid problem are too narrow on a functional level
Yes, T4 and TSH levels may indeed be 'normal' within the blood... but this doesn't automatically translate into efficient functionality
of the overall thyroidal system.
No surprise, therefore, that so many people suffering genuine thyroid dys
function (compared to mal
function) keep falling through the diagnostic cracks!
Still skeptical or doubtful about this discussion on the accuracy of blood-based hypothyroidism tests?
If you’re a doctor, perhaps the next time your patient presents with any of a range of hypothyroid-like symptoms, yet returns 'normal' TSH/T4/T3 levels, you might consider at least ordering a rT3 test (see link in blue box below).
Why not see what that result is, and then correlate it to the above information... as well as to that patient's presenting symptoms.
For those of you who have suspected an under active thyroid, but have been constantly fobbed off because your hypothyroidism tests keep coming back as 'normal', you now have a stronger and more empowering platform from which to renegotiate a proper diagnosis from your doctor - plus get adequate treatment
Further Topics Related To Hypothyroidism Tests
To explore other dimensions related to hypothyroidism testing, you might like to read further by clicking on the various links below:
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Links To Other Topics On Hypothyroidism
(1) - http://www.aacc.org/SiteCollectionDocuments/Archived%20and%20Historical/ThyroidArchived2010.pdf#page=1
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