I’m an adult with SWCAH, when i was young hydrocortisone didn’t exist so i was on cortisone. when i reached adult bone age (11yrs old) they switched me over to dex. Endos like to switch over to prednisone or dex because it’s more convenient. Prednisone is taken 2x daily, and dex 1x daily. They stay in your system much longer too. Prednisone 20hr half life, dex 56hr half life. So it’s easier to just hop out of bed take a pill and go off to college or work.  It’s easier too when you’re out partying at night clubbing when you’re a young adult and think you’re invincible, LOL. Plus prednisone and dex hinder growth in children.  I’ve been on dex for 18yrs now, i’m in the process of switching to hydro because it is chemically the closest equivalent to cortisol than any of the others and has the lowest half life (8-12hrs) therefore someone taking it won’t have as many of the extreme long term side effects of dex for example.  Being on dex for 18yrs now, my bone density is down 10%, i’ve been told i have fat deposits on my liver, i’m extremely obese, can’t lose weight, and have an uncontrollable appetite sometimes.  This is why i’m now switching to hydrocortisone, i would of done it sooner, but didn’t know it existed till recently.

So to fully answer your question, and i’m sure Carol M will agree with me here, there shouldn’t be any (physical) reason to switch to prednisone or dex in adulthood. The main reason it’s done is convenience and/or adults lacking in compliance in taking pills 3x daily (taking them to work with them, at dinners, parties, etc....) but in this day and age when everyone walks around with a water bottle and a vitamin box.  Society has changed!

c