Hair supplements

What are some good hair supplements to take? My hair is suddenly brittle, dry and feels thinner. I dont have any bald spots. My thyroid levels are slowly moving but not out of the normal range. My immune system attacks my thyroid but so far nothing enough to diagnose me with hyper or hypo thyroidism yet. My hair amongst other things are being effected. My doctor isn't too concerned but I can tell a difference with my hair. Any help is greatly appreciated.