@WBL:
You do sound frustrated, if you are still feeling unsatisfied you could contact Dr Jean Dodds, she has done wonders for helping dogs with thyroids disorders.
Here is a website that has contact info, and how to send in samples if you want
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If you have the results (full panel print out and you should be able to get that from your Vet) you can just send that to Dr. Dodd's, she will read the results and give you a recommendation… Don't really think that she is all that much better then others, however she does see many B Thyroid results.
I have sent her results from MSU and she agreed there was no need for supplements at that time.