It's quite normal for panda marked ones to be deaf.
 
This should help you:
http://wolfysluv.jacksnet.com/deaf.html
 
If anyone displaces that addy or needs other help great links can be
found in archives and other places with lists of links like
http://ferretcongress.org (crit links)
http://www.trifl.org/medical.html
http://www.ferretcentral.org
http://www.fothferrets.com/ferretinfo.html
http://fhl.sonic-weasel.org/
http://listserv.cuny.edu/archives/ferret-search.html  (Look familiar?
It should; it is in every day's header of the FML.)
 
I think that there may be past articles on the topic, too, in back issues
of "Modern Ferret" and "Ferret".
 
Yes, at times an infection, or a med can temporarily drop blood sugar
(hypoglycemia), but I can't recall of any causing more insulin to be
produced.  Someone else may have info on that score for us all.
Insulinoma is a VERY COMMON growth which decreases blood sugar by
increasing insulin output.  I think the best place for you to start to
learn about this and which meds are used (Prenisolone, Diazoide, etc.)
is the Miami Ferret site
http://www.miamiferret.org/fc
which has a large amount of info delivered clearly.
 
There was an excellent article by Dr. Bruce Williams on this in
"Ferrets" which is available as a PDF at
http://www.afip.org/ferrets/index.html
and which should be useful to show your vet.
 
Those are good places to start reading.
 
Finding vets who are dcently informed about ferrets:
Moxie, some of those addy early in this post have links to vet search
sites.  Also useful for that area may be looking in
http://www.supportourshelters.org
[Posted in FML issue 4441]