I agree with @Ema
that the signs and symptoms are very important, as sometimes labtests fail to show thyroid problems.
I can attest to this. My blood test showed normal in all thyroid parameters and yet I am convinced that I am hypo.
Atleast according to Ray Peat, a couple signs of hypo would be low CO2 levels and high estrogen levels. I have both of those. Also body temps and and pulse bpm's may not always be that predictive. According to him, norepinephrine can be raised which will help in keeping temps and bpm's up to compensate. Haven't taken my temp recently, but anytime I have, they have been normal and sometimes slightly low, but never low enough to alert me to being hypo. As far as my resting pulse bpm's, they have been consistently around 85 bpm's. And according to Peat, a more predictive measure would be the Achilles heel reflex test, where if your leg on return comes back slowly like a nuismatic door closing. When doing this to myself, mine does the same.