My opinion based on lots of reading about different criteria is that this is a pretty normal stimulation test. You doubled from baseline and your baseline went over 20. However, I would say that I have come to understand that people with AI sometime "pass" their stim test, but are later diagnosed when it is repeated and then they fail.
11.7 is considered in range, yet some would say that a healthy morning cortisol should be close to 20. So, although there is not conclusive evidence of AI, you may need to still keep this as a possibility if you continue to have symptoms, develop more symptoms consistent with AI, and remain undiagnosed. It can be a tricky diagnosis with waxing and waning and a slow, progressive decline. So, I guess what I'm saying is that if you continue to have symptoms that suggest AI, you may need to keep this as a possibility in your mind even if a physician is telling your all is well. Unfortunately, this disease is rare enough that many physicians just don't know enough about it and it can take a persistent patient to get a diagnosis.
Another way to evaluate adrenal function is to look at aldosterone, renin, DHEA-S and a metabolic panel to check sodium and potassium. Those are just basic blood serum tests even your GP can order, without the help of a endo or any other specialist. However, if the question is that your may have secondary A, in light of your previous prednisone use over the years, then those would be normal in that situation.
Since you have a history of autoimmune disease has your thyroid or other glands been tested, which might explain your lack of energy? Best of luck to you.
It looks normal to me as well. Normally you have to have a sodium issue to have a cortisol or renin/aldosterone issue, and also low blood pressure etc.
Fatigue is very difficult to pinpoint!