Being prematurely grey is a risk factor for autoimmune thyroid conditions.
I don't know if the hair goes back to normal after treatment.
Others will be along with more to offer....
I am glad some one asked this question. I am just 35 years old man and pretty most of my hairs are grey plus fallen as well. Surprisingly my chest hairs/face hair are mostly grey . I have diagnosed Hashi/Hypo in 2006 but my grey hairs since i was in late 20s . I am sure grey hair is related with autoimmue thyroditis.