I want to ask others something, because the immediate conclusion seems so stupid it can’t be true.
As I have understood it, and I must be wrong, local reference ranges in endocrinology are set by measurement of local populations. But, at the same time, an individual’s personal set point varies very little (in regard to thyroid hormones anyway).
So, I was born in Scotland. I don’t know what the local range is, although I could look it up, but say the range for ft4 is 12-22.
When I was 30, I moved to London. At that stage, my endocrine function was fine and had never been tested. It was only measured here after I became ill, and my ft4 was first measured at 12, declining over time to 10. Ft3 began at 4.50. Declining to 3.50. My tsh was always 0.1 or less.
Now this is the bit I don’t get- would my ft4 be low in Scotland but ‘within range’ in London (local range 9-22)?
I must have missed something, but what?