Thanks for the informative reply.
>The same machine that does all the other thyroid tests does the FT3 as well.
Oh I see. I wasn't aware of that. It seems odd that laboratories would continue to measure total instead of free thyroid hormones. Do you know the reason? Is the kit/control more expensive?
>This cost is then, I think, the problem with GPs - they just will not shell out for the tests.
'TFTs' are requested frequently, but GPs do not always specify precisely which tests they want. In cases where specific tests are requested, it seems to me that the choice of tests is influenced both by the laboratory and by conventional medical teaching, but cost might also be an issue. Also, I do know some labs offer different sets of tests (when 'TFTs' are requested) based on the clinical information provided. Others amend the profile of tests offered according to the TSH result.
>Any test that is run just the once a week is expensive
According to the Association of Clinical Biochemistry (2006), 10 million tests are being requested annually in the UK at an approximate cost of £30 million. Apparently, some labs are finding it difficult to cope with the increased number of requests.
>I can't see the point of doing all the other tests - the FT3 is the metabolite which is active at tissue level and that is the one that matters.
Tests for TSH, fT3, fT4 and thyroid autoantibodies all have value. The value of each individual test or combination depends on the circumstances. None of the tests in isolation are adequate to make a diagnosis. TSH alone may be an appropriate screening tool when thyroid disease is possible but unlikely. A combination of tests is initially needed for any patient who presents with probable thyroid dysfunction.
During the early stages of thyroid gland failure (for example due to autoimmune disease), TSH is frequently the only test to reveal an abnormal result. fT4 and fT3 are usually still within the normal range. Only once the disease has progressed somewhat do the levels of thyroid hormones go down. This is because in early stage disease, the increased levels of TSH are successful in bringing the concentration of thyroid hormones back into the normal range (compensated hypothyroidism). Measuring levels of free hormones but not TSH could lead to a delay in diagnosis. TSH levels are also needed to distinguish between primary thyroid disease, pituitary disease, and sick euthyroid syndrome.
>Most GPs are very poor diagnosticians these days. Back when there were no 'confirmatory' lab tests, docs had to listen to their patients symptoms.
Lab tests are often useful, but I'm also concerned that an over reliance on such testing has led to a deterioration in other skills, particularly physical examination. I appreciate that GPs usually have little time but I wonder whether the reduced tendency to examine patients properly has actually led to loss of this skill.... and not everything shows up on a blood test! I distinctly remember going to the doctor feeling very unwell a couple of years ago - no examination of any kind was performed, not even pulse/BP. In some cases, lack of diagnostic confidence leads to overprescribing of medication, particularly antibiotics.
>Big Pharma could make loadsa money off Levo!
Perhaps they did, and continue to do so in some countries, but this doesn't explain the current situation in the UK. Levothyroxine is predominantly sold by generics manufacturers (except for Mercury's Eltroxin which is also cheap). Big pharmaceutical companies do not sell or advertise levothyroxine in our country. Generics companies do not advertise levothyroxine at all.
Treatment based on T3 or dessicated thyroid is unlikely to really 'take off' in the UK unless the British Thyroid Association changes its stance. I think this would require a major clinical trial, possibly two. Most trials performed so far have not shown an advantage for T3/T4 combination therapy over T4 alone. I do wish doctors would keep more of an open mind though, and assess patient's individual response to treatment. I think this is one of the benefits of going private. The consultant may be the same but you get the time and consideration which makes all the difference.