I've Been Treated For Hypothyroidism For Over 20 Years (I'll

I've been treated for hypothyroidism for over 20 years (I'll be 50 in a little over a month.) I was just tested for Hashimoto's and told that yes, I have the antibodies for it. What is the difference in being treated for one vs the other? Does it make a difference that I haven't been tested for Hashimoto's before? After reading about it, I don't see a difference in treatment or if anything will lessen the symptoms I still have.