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.