From an older interview when the "normal" tsh range was higher-
"The TSH usually is somewhere in the range between .5 and 6 units, and a person will be called normal when it's anywhere in that range. But when it's above 1 unit, in other words when it's just anywhere above the lowest normal range, the TSH is already causing excess production of the mucopolysaccharides that tend to load up the various tissues. "
Ray Peat 1996 interview
"The TSH usually is somewhere in the range between .5 and 6 units, and a person will be called normal when it's anywhere in that range. But when it's above 1 unit, in other words when it's just anywhere above the lowest normal range, the TSH is already causing excess production of the mucopolysaccharides that tend to load up the various tissues. "
Ray Peat 1996 interview