I can remember only a handful of ferrets mentioned during the 18 years
the FML has existed ever having fur loss that turned out to related to
allergies instead of adrenal problems (with or without allergies also
present) and then they tend to scratch the areas bald so it would not
be likely to be like the undercoat fur loss you mentioned that you are
seeing which is more consistent with adrenal neoplasia as are the
behavioral changes you mentioned.  (Loss of fur on the tail alone is
usually only a skin problem but loss on the trunk is usually adrenal.)
(More common seems to be fur loss from long term Prednisone/Prednisolone
use in a few ferrets, but that isn't common, either.)
 
There IS a way to test the allergy hypothesis: call your vet to okay the
use of a antihistamine with a proven record in ferrets such as plain (no
other meds added) pediatric Benedryl elixir.  If there is no strong
response (Minor changes won't mean anything.) then discount allergies.
 
BTW, itchy skin is common adrenal symptom as well.
 
Yes, a person can take all of the precautions you took and still have
adrenal neoplasia show up.
 
Here are some adrenal symptoms.  It is not a full list, nor do ferrets
need to have more than one symptom to know that adrenal neoplasia is
present.  Some are completely asymptomatic.
 
        Bilateral fur loss on trunk
        Swollen vulva in females
        urinary tract infection
        swollen prostate
        dysuria (inability to urinate -- dangerous)
        anemia which can become fatal
        behavioral changes consistent with more sex hormones circulating
                    (aggression, babying, nurturing, etc.)
        thin skin
        itchy skin
        certain skin sores
        an increasingly pear shape (thin upper body with fat in abdomen)
        strange fat dispersion (even very rarely inside thorax --
                    dangerous) etc.
 
Our personal experience (which I have heard echoed by more than a few) is
that ferrets with head blazes or white heads are more likely to have some
medical problems earlier.
 
Here are two options short of surgery which we have done when ferrets
have questionable cases:
 
1. the Tennessee Panel test can be used.  Downsides: it isn't run often,
it is expensive, it can miss early cases (Been there.)
 
2.  a Lupron shot can be given.  It should not be a weak one, and if your
vet doesn't have a lot of this around then the best approach economically
will be to go through a compounding pharmacy (many of which ship):
http://www.smartgroups.com/vault/ferrethealth/ReferenceShelf/comp_pharm.html
 
Your vet must follow the storage info or the compound won't have a
chance of working.  This IS expensive but it will also control the
symptoms for a while and some vets think that some cases of neoplasia
can be temporarily reduced with it.  It is med for adrenal growths when
the ferrets are not surgical candidates.  (If you go to
http://www.sonic-weasel.org you can also find past vet posts on meds to
add if prostate problems or anemia are present.  These may also be in the
FML Archives but I think at least one carried over post may be too new.)
The Lupron shot will give you more time if adrenal neoplasia is present.
We've used it successfully to delay surgery when we had family members so
ill that we could not trust our schedules enough to have surgery safely
done soon.  (Of course, that won't work if a malignancy is present but
luckily most adrenal growths aren't malignant.)
[Posted in FML issue 4246]