Does the same pediatric endocrinologist read the bone age every time?  If not, it’s very likely that one of the bone ages was wrong.  It’s really more of an art than a science and for comparison over time the same person should read it and it should be a pediatric endocrinologist.  Also, I think she should have it done every six months.  Hopefully the 8.5 was wrong and not the 8.1!