This article will be very, very, very (Did I remember to say "very"?)
useful for you:
 
http://www.afip.org/ferrets/PDF/insulinoma.pdf
 
and
 
http://fhl.sonic-weasel.org
 
will also help.
 
Prednisolone tends to be more effective than Prednisone if there is also
an liver damage (because Prednisone needs a liver processing steo to be
turned into Prednisolone).  Pred should be given with food twice a day
(sometimes 3 times a day if the sugar balance becomes hard to maintain.
 
To try Diazoxide (Proglycem generic) to see if it will help with your
little one try a trial by using a compounding pharmacist used to ferrets.
Many of them ship.  You can find a list of such pharmacists in
 
http://www.smartgroups.com/vault/ferrethealth/ReferenceShelf/
comp_pharm.html
 
Surgery can be useful.  There is a marvelous write-up on this surgery
in Dr. Rosenthal's column in the latest issue of Ferrets Magazine.
 
Sukie (not a vet)
 
***** Here is a very unexpected dietary research study result which I
am sure will be looked at more carefully in further studies (which is --
of course -- exactly what needs doing before drawing conclusions based
upon one study or upon the even weaker basis of a hypothesis) :
 
*****  http://www.sciencenews.org/articles/20050611/food.asp
 
*****  For those interested in microRNA and malignancy:
 
*****  http://www.sciencenews.org/articles/20050611/fob1.asp
[Posted in FML issue 4905]