The last part of the Tennant piece may be of interest (its taken from his newest book, Cancers On/Off Switches). I figure that you know most of this basic info but---
He stresses, which you may already know of course, that the ratio between the free T-3 and the RT-3 is very important to really know how much T3 is available and also that if certain "stressors" are activating than we will still suffer from Hypothyroid symptoms. Thus while blood levels may be acceptable, cellular activity may still be depressed.(as you mention the temp of the xtremities).
Furthermore he states that the family MD is usually relying on TSH and total T4 levels, missing other important factors.
"---we can see that the lab results for TSH that most doctors rely upon to diagnose and treat hypothyroidism uses lab “normals” that are over ten years out of date. In addition, most doctors are unaware that TSH is managed locally in the pituitary by a different enzyme system than at the cellular level---"