Stumbled across this article about hypothyroidism treatment paradigm shift:
This article says something about TSH I had read on a pharmacist.com article some years back. Although the low end of the TSH scale defined by "official" groups is 0.3-0.5, a Scottish study determined that there is no risk of arrhythmia or reduced bone density, so long as 0.04<TSH<0.4. So given what functional medicine has said about TSH upper limit, it appears the "normal" range should be something like 0.1<TSH<2.0. The article implies (but does not explicitly state) that TSH should not be used for diagnosis.