Are you getting any treatment for your thyroid problem? I believe that once you get the thyroid under control, you may see new hair growth.
It helps if you take daily multi-vitamins, keep your hair clean with as least harsh shampoos as possible, keep the hair conditioned to prevent breakage, eat healthy, drinks lots of water to help keep the hair from becoming brittle, do not try to comb or brush wet hair as it is more fragile, avoid excessive heat or products on your hair, and try to avoid stress. All of those things will help.