For me as a working scientist, this forum is a rich source of data regarding the normal ranges that different hospitals use for TSH, FT4 and FT3. And what utter confusion there is! Perhaps TSH ranges are somewhat more harmonious, but only somewhat. The quoted FT4 and FT3 ranges however are enormously variable from source to source. For FT4 you might have the lower limit anywhere from 7 to 10 and the upper limit 18 -25. FT3 lower limit 3 - 4.5 and upper 5.5 - 7.5. Since the human race is exactly that and doesn't significantly differ from place to place, differences of 30-40% in range limits for FT3 and 25% for FT4 simply is unacceptable. How patients moving from one hospital's tests to another's get sensible answers is quite beyond me. This has been a rant of mine for 30 years +, that the thyroid profession is complacent and truly ignorant about the tests it so mechanically relies on. Until some degree of rationalisation and consistency is brought about, no wonder misdiagnosis is as prevalent as it is, let alone the basic misunderstandings about ranges in therapy. Goalpost thinking when using range limits simply adds to the confusion. However, this forum's information is extremely useful in gathering experience of these range variations together and I can use the info very usefully in other forums.
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