For a short time the Americans changed the reference range for normal TSH. Unfortunately the labs didn't follow up and Drs objected so they abandoned it. Details here, it's much narrower than the usual and is meant to flag early onset of hypothyroid disorders.
Apologies if this is old news: TSH reference range - Thyroid UK
Apologies if this is old news: TSH reference range
This very hard for me to understand, lowering the range results in more people getting diagnosed -> let's not lower it and magically these people return healthy. It's illogical, stupid and ridiculous.
If according to studies TSH <2 or 2.5 indicate problems then keeping the range at 0.4-4 or 0.5-5 does not make it go away. Same amount of people continue to go undiagnosed.
Lowering the range does not cause illness! !!!!!
Over here in Finland university hospital has adopted range 0.3-3.6.
Synlab which is European lab, NHS uses it too, unfortunately I do not know what tests NHS buys from them has 0.4-4 range, but they advise that TSH < 2.5 should be monitored as it indicate thyroid issues. That's in finnish manual, but surprise surprise can't find manual in English.
Over here in Finland most labs actually do support lowering TSH, they advise how to interpret thyroid tests and when to retest. Many laboratory technicians / nurses do know TSH is quite irrelevant and some doctors agree that laboratory technicians do know better than doctors.
So sad. And the situation is even worse in the UK, where doctors like the TSH to go up to 10, no matter what the range! I've never been able to see the logic in that - why bother to have a range, in that case. But, so many people left suffering needlessly. The medical profession should be ashamed!