I think your bone density will improve with the switch to hydrocortisone myself.  You will have more exposure to the hormones that favour lay down of calcium in bones and increase bone density.  This was one of my concerns about pred treatment really.  I am not going to switch to it.  Not for night time use anyway.  I don’t even like it for day time use actually.  I will not be pushed around on that one.  I know exactly what it causes and i think other parents need to be educated more, as well as Doctors.