I'm not an expert on adrenal disease, but your description sounds familiar.
I've read reports from other people on the FML about ferrets intermittently
feeling lethargic and then energetic, intermittently losing hair and then
growing it back again. Also, I'm pretty sure that not too long ago, one of
the vets on line (either Dr. Williams or Dr. Weiss) posted that just
looking at the adrenals may not be enough and a biopsy may be necessary.
They tend to go more by the symptoms, if I understood them correctly.
Hopefully one of them posts a response -- you are definitely not a paranoid
mom (in my opinion) to be worried about your fuzzy. After all, who else is
going to worry about them if not us big people?
[Posted in FML issue 1338]