And, for those few who are not surgical candidates, here is a post by
Dr. Jerry Murray which was part of a conversation on this topic:
 
>Sorry I was not able to answer these 3 questions earlier.  The reason
>Lupron is kept frozen is because the product does not contain any
>preservatives.  In humans they mix it up and inject it right away;
>however, it is not possible to do that with ferrets.  Thus it is stored
>in the freezer and taking out as needed.
>
>The another question was about Lupron actually shrinking the adrenal
>glands.  I agree with Dr Williams' surgery is the best option if the
>ferrets is healthy enough for surgery, and the owner can afford it ,
>etc.  However I do think in SOME cases Lupron can indeed cause the
>adrenal gland to become smaller.  I think these are hyperplasia and
>adenomas that become smaller after using Lupron.  Again the key word is
>some.  This does not happen all of the time.
>
>Lupron once a month vs. Lupron every 4 months.  These are the same
>drug.  Just in different slow release version.  The 4 month version is
>typically sold in 1mg and 2 mg sizes for ferret use.  That would be
>equal to 0.250mg monthly and 0.5mg monthly (1/4=0.250 and 2/4=0.500).
>The 0.250mg =250mcg and 0.500mg=500mcg.  Thus you have to compare that
>actual amount of Lupron being used on a monthly basis to compare the
>two.  I personally use and like the once a month version.  That way the
>ferret is rechecked each month, and any changes can be made if needed.
>Changes such as increasing the amount of Lupron if needed, adding other
>medicines such as melatonin, Propecia for prostate problems, and
>Arimidex + Epogen for anemia problems.  Plus if any new problems
>(insulinoma, etc) develop they can be treated quickly.
>
>Hope that helps,
>Jerry Murray, DVM
[Posted in FML issue 4266]