BUT, Isn't Hashi's a total or near total version of the most extreme for a hypothyroid condition? I'd gone from definite Hypo[damaged] to definite Hashis [essentially non-functioning thyroid] When I recently had auto-immune tyroid testing the numbers were high, but not outrageous...probably modified by IVIG infusions for other issues.
Because in my case, the thyroid appeared to be in control thru synthroid, with only one 'episode' right after the auto-immune onset, and the tests were fairly basic [tho resulted in a dosage change...upwards] No professional ever put the two-and-two together... Hindsight is wonderful-sort of.

Only things I can think of...and these options are both hard: first, find another doc and get a second opinion. Second, challenge this doc about WHY he feels you have gone from one extreme to the other Ask him for facts for his opinion -gut feelings here or biases against your taking the dessicated route should NOT be the 'factors' for decision making. If it takes an auto-immune thyroid panel to prove one point or the other, at least you have 'back up' paperwork to the pros and cons. Another possible tack would be to ask your OTHER docs about this quandry. Sometimes different minds and/or peer pressure can do wonders [has worked for me at times, not all tho]

While we all would like to take the lowest doses of everything we take...at times we have to take more to get on with life. Asking questions is a cheap alternative to being sick! This doc could possibly be doing harm for his opinions? That should be questioned and thoroughly at this point. It's more important to protect yourself and prevent further damages and backslides.

I definitely wish I could suggest more/better options. None are fun. But, WE have to work the 'systems' as best we can to our advantage -not to archaic philosophies that change daily to our detriment. I sure wish that I was a fly on the wall during those visits tho....Hope this helps? - j