I guess it depends on the severity of the break and the severity of the CAH.  My daughter has broken many bones in the past (she is now 17) and we never have given the shot.  We have stress dosed her as quickly as possible and that worked for her.  Having said that, there are other times when we had to give the shot - vomitting and  dehydration, for example.  I would talk to the endo and see what he/she has to say.