If u r looking for an L50 for each supplement, then look at the clinical trials.
As far as what the maxiums are for treating thyroid dysfunctions, u would have to look at what Dr's, such as Brownstein and Flechas, came up with for the thousands of patients they have treated.
If u have the money for a clinical trial, u can find anything you want.
My point is that we are ALWAYS learning and there are no absolutes.