Nobody is going to like my suggestion.
I am also hypothyroid and suffer from a thin, parched, frizz fest where once I had masses and masses of fine stranded, but wavy and abundant hair.
I have tried EVERYTHING. Highlights, protein, plopping, no poo, moisture masks, etc etc etc. All high action and multiple process efforts.
None of it worked and I just remained a completely parched and dry frizz beast.
Now I splootch the mids to ends in lots of pure almond oil and comb that through to the ends and that done, I wash it ONCE a week in warm water only and let it air dry. Zero detergents.
That is it and now it looks relatively normal again. Madly, even being this radical and hands off, it still gets a bit dry mid week on the ends (with NO washing) and I touch the ends up with MORE almond oil and tie it back in a low pony until the oil has taken hold on the ends and penetrated the frizz.
Works for me. It's insane just how dry and screwed hair can get with hypothyroid and menopause combined. I feel your pain.