Hair loss is associated with being hypothryoid, and you are certainly that! It is unfortunately a scary and depressing thing, to think you might go bald and never grow hair back again, but rest assured, it is extremely unlikely to happen.
It may not be the Synthroid causing the problem... thyroxine is the main ingredient no matter which synthetic thyroid replacement you take. More likely you need a higher dose of the hormone.
The endo may have thought you no longer needed any medication as your levels may have been fine. Often with goitres, when they shrink the doctors will stop medication. If the goitre grows back they put you back on medication. Often they do not grow back , after having the medication shrink it. I do not know if you had an enlarged thyroid.
It would be really great to see your latest results of lab tests. Ask for a copy and post here what they were. Often doctors say Oh, you are normal...when in fact yo ure hypo or hyper thyroid.
You may not be converting the Synthroid in your body effectively and keeping you at hypothyroid levels, too.
As I said, hair loss is normal (if you want to call it that!) and you may not be on enough medication to stabilise this problem..and yes..your hair will grow back.just takes a while..Hair grows at 3mm a month..which is really not much.but be patient.
Cheers
Have you ever asked to be put on something other than synthroid? There are other drugs out there. I'm hoping that I don't have this trouble on synthroid, but if I do, this time I will not hesitate to say so. Maybe the new endo will suggest something.