Dear Pam:
 
>THANKS, as always, for your help.  Yes, given the trace ketones, we've
>stepped up the pred weaning and she'll be off of it in less than a week.
>A vet on another list suggested I stop it cold turkey, but others have
>warned of problems with not weaning it gradually away... a bit frightening
>to me... Your point that insulin and pred can be used at the same time,
>but with difficulty, helps ease my mind a lot.
 
After the time Sonic has been on it, a week is close to cold turkey -
although we know that in most individuals, long-term pred does not result
in adrenocortical atrophy, as it does in other species, you don't want to
take the chance that Sonic is one of the rare few who has had adrenal
changes.  We'll know in a week.
 
Doing some reflection on this problem, it seems that taking Sonic off the
pred and proglycem (can't remember if he is on it or not) is probably the
best first step in treating this case.  While this is still an unusual
circumstance - an insulinoma ferret progressing to diabetes - there are a
couple of explanations.  One is that we have over-administered prednisone
and proglycem to the point that we have caused diabetes.  We know
prednisone counteracts hypoglycemia in two ways - by increasing the
production of glucose in the liver, and secondly, by causing insulin
resistance at target cells.  PRoglycem decreases insulin release by islet
cells.  I would submit this as the most likely cause of those rare ferrets
on long-term prednisone and proglycem resulting in diabetes - we have
caused sufficient systemic insulin resistance and inhibited the release of
insluin by the tumor and the normal islets that we have created a diabetic
state.
 
There are a couple of other possibilities, but they are far less likely.
One would be chronic pancreatitis, resulting in loss of the insulinoma and
sufficent islets to have low levels of insulin and diabetes, and the second
would be the rare production of amyloid in the tumor.  Amyloid is a protein
that we seen occasionally in both islet cell tumors and in normal islets
whose presence eventually results in significantly diminished insulin
production.  Of course, the possibility of glucagonoma is always there -
not to say that a ferret can't get it, but I have yet to see one, and I've
looked for them in such cases.  (Yes, I do use immunohistochemical stains
which are specific for the various pancreatic hormones - insulin, glucagon,
somatostatin, etc.  when I come across insulinomas which have an aberrant
clinical profile - such as yours.)
 
I think that it is key that we dclosely monitor the blood glucose as we
decrease the drugs, to make sure we don't fly down into the hypoglycemic
state again.
 
At any rate - this sounds like a very interesting case.  I've got my
fingers crossed for Sonic, and in case that is not enough, I've got the
immunohistochemical stains at the ready...
 
With kindest regards,
Bruce Williams, dVM
[Posted in FML issue 3262]