I know this is an old thread... but I had Cushing's disease which is basically too much hydrocortisone. You can get it from taking steroids (then it is called Cushing's syndrome) but mine was caused by a pituitary tumor.
My tumor was discovered in 1992. I was not heavy then. But over the years, I came within 6 lbs of doubling my body weight (as well as other horrible symptoms). I had my tumor out in 2004. It did not cure me and I had to have my adrenals out in 2006. Adrenals are where cortisone is produced in the body. Now since I am cured, I have lost about 65-70lbs, but my muscles are... wasted. We thought it was from the Cushing's. Now I may have MG (had an abnormal EMG and waiting on other tests). My own body's overproduction of steroids may have been masking this?

The first thing out of my neuro's mouth was - oh well we can give you prednisone. NO WAY. I need to lose, not gain and not get any weaker. I just got my cheekbones back.