Zoe:
If you have low cortisol, you could go into an Addison's crisis and die. Even if you do have the adrenal problem because of asthma medication, you still need the extra cortisol. Sometimes you can wean off of it slowly with time if your adrenals starts to kick in again, but sometimes you can't. It seems to me that they are taking a terrible chance taking you off the cortisol. Get to another doctor, fast! Get an ACTH stimulation test to find out if your adrenal glands are working. Then have a full workup of your thyroid and growth hormone levels. My problem was pituitary failure, and it took several doctors and me thinking I was dying (loss of 30 pounds, blood sugar crashes, low blood pressure, dehydration, nausea, vomiting) before I finally stumbled across a doctor who knew what he was doing. You need help, girl! Stand up for yourself and get it before it's too late!