In all honesty I believe its a bit of a fix all metabolically. I was very hypo when I first came across Rays work but I couldn't get NDT to work. I'd take it for a couple of weeks then start getting achy legs. It was making me more hypo as I assume at that time I wasnt converting T4 to T3 efficiently.
Progesterone bypassed this problem immediately raising thyroid for me. It also shrunk a small lump in my neck the docs told me was harmless. Not sure what it was but I assume it might have been anything from a small cyst to a goiter or a thyroid nodule. Its completely gone now. My temps rose within a few days of starting progesterone.
We ought to aggregate all these thyroid success stories somewhere. They would illustrate how complex things can be, and give people ideas. I wonder what Broda Barnes would have done with you when NDT didn't work.