Agreed. Some sort of 24-hour continuous thermometer attached while you slept might be good. And ideally you want to measure skin temp and outside temp, since what we're interested in is the amount of heat passing through your surface, not your temperature per se.

But Barnes reckoned axilliary waking temperature was the best test, and he was a proper endocrinologist with access to whatever tests he wanted, and he looked at lots. And everyone thinks he was a loony because he said hypothyroidism was really common and explained everything. And I did too until I realised I'd just predicted the same thing from the simplest explanation for my mystery.