Update: I've tested Thylexan, same dose as Tyronene (20 mcg/day, 10 mcg before test). TSH was now suppressed to 0.02 (as compared to 0.10 on tyronene) and cholesterol was a bit lower than with Tyronene (5.3 as compred to 5.5). So Tyronene seems somewhat less potent than Thylexan, but there are other variables involved, like warmer weather & being out in the sun more often, so I can't say anything with certainty.