Very tired and thin hair

I am an 18 year old female. I have recently noticed that I am very tired and take frequent naps even after 7+ hours of sleep. My hair is also very thin at the top near my scalp and I am very self conscious about it. My hands and feet are also always cold. Could these be symptoms of a thyroid problem or something more serious? OR should I just conclude that it is because of stress, (i am a busy university student)