What does having a slightly elevated thyroid level mean to a teen with anorexia?

Some imbalance or...: Depends on the big picture. In a normal person, a slightly elevated "thyroid level" may be normal (that's how life works; lab reference ranges don't always mean normal vs. abnormal). Anorexia is not normal, regardless of whether it is due to anorexia nervosa or some other disorder. Therefore in this case, there is more likely a thyroid hormone imbalance that will benefit from treatment.