+1 silica for hair growth.
OP: Is it possible that such extreme hair loss is actually related to an essential fatty acid deficiency? That was what was causing mine. It got so bad that I didn't want to (and didn't!) brush or wash my hair. I'd be in tears in the shower and the drain would always be clogged up with all my (formerly beautiful, long) hair.
I don't know specifically about Hashi's, but thyroid dysfunction usually results in hair thinning in general (hello, outer third of eyebrows, I miss you!), but I am wondering about massive rapid shedding like yours. Has anybody heard of this?
Once I started eating fish (was a vegetarian), my hair shedding stopped virtually immediately....but because I still had the underlying hypothyroidism, was still thinned as it grew back in.
Have you happened to have major surgery recently?
"Let food be thy medicine and medicine be thy food." -- Hippocrates