Hypothyroidism Diagnosis and Thyroid Blood Tests

Primary hypothyroidism is usually detected when numerous symptoms begin to appear, which prompt the patient to seek medical advice.

As the thyroid gland is no longer able to adequately respond to the demand of TSH, this usually results in lower than normal levels of T4 and T3 appearing in thyroid blood test results.

In addition, TSH levels are often higher than normal. This is because the pituitary gland is attempting to stimulate more thyroid hormone production by releasing more TSH.

One of the most common causes of primary hypothyroidism is an autoimmune disease known as Hashimoto’s thyroiditis or Hashimoto’s disease. This is when the immune system attacks the thyroid gland with autoantibodies and gradually destroys it.

The levels of TSH, T4 and T3 circulating in the bloodstream can all be measured by routine thyroid blood tests. 

The most frequent (and best) way to test thyroid hormones by blood tests is to test for free T4 and free T3 (or FT4 and FT3). These are the portions of T4 and T3 that are not bound to circulating protein. They are the free forms of the hormones and the only form that is able to actually do anything. Hence it is more useful to test for these than the total T4 and total T3.

It is advisable to have the autoantibodies TPO and Tg tested in order to know for sure whether the thyroid problem is Hashimoto's thyroiditis. If it is 'Hashi's' then it is quite likely that over time the thyroid gland will be slowly destroyed.

Knowing whether the TPO and Tg autoantibodies are elevated is vital for two reasons. Firstly, it may be possible to take actions to slow down or stop the thyroid gland destruction by calming the immune system. Secondly, it is important for anyone with Hashi's to realise that his or her thyroid medication will need to be adjusted over time to compensate for lost thyroid function.

Anyone who has been told by their doctor that they have a thyroid problem but they don't need to have the full range of tests (TSH, FT4, FT3 and autoantibodies TPO and Tg) should insist that they are done. They also need to obtain the detailed results, the units that these results are expressed in and the laboratory reference ranges. If the patient does not feel supported they should consider changing their doctor.

At the diagnosis stage of thyroid disease, when a thyroid problem is suspected, then the full range of thyroid laboratory tests will enable the type and scale of the thyroid problem to be properly assessed.

Sometimes, when someone doesn't feel well and they have routine thyroid blood tests run by their doctor, they may be told that they have 'sub-clinical hypothyroidism' or that they have a possible thyroid problem that will need to be watched in the future.

Sub-clinical hypothyroidism is a medical description that means that the person's TSH is a little higher than expected and their FT4 and FT3 levels may be a little lower than expected. Frequently, the advice from doctors is to wait and see how this develops. In some cases, the patient's thyroid hormones may simply return to normal and the test results may have been as a result of a spurious laboratory test or something that neither doctor nor patient will ever discover.

However, in many cases this is just delaying the inevitable and therefore preventing the prescription of any medication that may help someone feel better. This is a further reason to insist on having the autoantibody tests TPO and Tg. If these autoantibodies are elevated then sub-clinical hypothyroidism is highly likely to develop into full-blown hypothyroidism and the sooner the person is on thyroid treatment the better.

A thyroid problem is serious and people need access to all the information that tells them exactly what the nature of their problem actually is. It is also important to actually get these results on paper: with each result, the units it is measured in and the laboratory reference range used for each test.

Once hypothyroidism has been diagnosed, adults will usually be given a daily T4 replacement dosage of between 50 and 200 micrograms. This sometimes works and sometimes doesn't work - but that's not what the medical profession will tell patients!

However, having thyroid lab test results that simply fit into the wide population ranges is no guarantee of being healthy. The ranges are too wide and once someone develops thyroid problems they may need different levels of FT3 and FT4 compared to when they were well. It is an entirely different situation once someone has thyroid hormones issues.

I can say a lot more about thyroid blood tests and the diagnosis of hypothyroidism in all of its forms. A huge part of the 'Recovering with T3' book focuses on this vital topic.

I will cover this in various places on this website and it will come up time and time again in any blogs that I post.

For those who wish to really understand what thyroid blood tests can and cannot reveal then buy the book 'Recovering with T3'. It will open your eyes to the scientific facts about what can and what cannot be concluded from thyroid blood test results.

However, comprehensive thyroid blood tests are essential during the diagnosis stage of thyroid disease - theyjust need to be used with intelligence and in a secondary role to the patient's symptoms. FT3 is the single most important blood test, as this has been shown to track patient's symptoms during treatment better than any other lab test e.g. better than FT4 and TSH.

Success Story

It's like a light has been switched on for me. I can think straight, I feel energetic, I sleep better, my body weight is levelling and my husband and daughter have their wife and mummy back!