I've sent Lyn Mynott a copy of a paper where we describe a new method of getting a better fix on the TSH reference range. Some of you have asked for a copy, but you might find it very technical (it is). I'll try to describe in short what we've done and the advantage over the classical method. The classical method simply plotted all the TSH values in a euthyroid population as logarithmic values and made a graph relating the frequency of finding patients at a particular TSH value over the whole range of TSH values. What you get is a very skewed distribution down towards the bottom end of the range with most people clustered about 0.6-1.5 and with a long "tail" of a few people stretching up towards the hypothyroid region with numbers going up to 3.5 and beyond. The problem with this is that these few people's results have a very big effect on setting the top end of the range, especially if some of them are doubtful in diagnosis. But by good statistics you can't ignore them if you don't have a good reason for doing it. Our new method gives a lot more power to the many people in the midrange rather than the few I mentioned before, and it shows clearly where the hyperthyroid or hypothyroid subjects' TSH values diverge from the euthyroid line, thus defining where the euthyroid range should end. So the method is based on more powerful statistics that minimises the effects of what might be aberrant wrongly diagnosed patients near the hypo end of the TSH spectrum and maximises the majority. Hope this helps those who read the paper.