With Medication. Hashimoto's disease is an autoimmune destruction of the thyroid gland (painless). Lymphocytes enter the gland to cause inflammation and scarring. The damage is usually permanent. Fortunately, with the availability of thyroid hormone replacement, levothyroxine, it is a very easy condition to manage- 1 pill daily. It can take weeks to feel better after starting medicine, but it works!
Variable. It is hard to give a time frame: as soon as 6 wks as long as 6 months.