My 13 yr old son is having the same growth issues.  He is 4’10" tall and weights 100lbs.  Our edno suggested switching from Cortef to Medrol - he seemed to think it’s possible that certain medications’ effectiveness can "plateau" (my son has been on Cortef since he was 10 days old).  We have gone through 10 months of adjustments - up & down & up & down - however the 17ohp & renin seem to be right where we want them now.  So, by all means, talk to your endo!