Mike hit the nail on the head.  Melatonin is the natural hormone that
directly and indirectly starts (in spring) and stops (in the fall) the
ferrets naturally breeding cycle.  This is in response to the photoperiod
(amount of daylight).  During the short days (fall/winter) more melatonin
is released which stops the breeding cycle.  Plus the ferret gains weight
for the winter and puts on its winter coat.
 
During the long days (spring/summer) less melatonin is released.  The
ferret losses some weight and put on its summer coat.  In adrenal gland
disease, the adrenals are acting just like the testes or ovaries because
the adrenal glands have LH receptors.  Melatonin lowers LH, so the adrenal
glands are not stimulated to overproduce the sex hormones.  Thus the
ferret gains weight, puts on its winter coat, and the adrenal gland stops
overproducing the sex hormones.
 
Lupron is a synthetic analog of GnRH which stops LH (and FSH) from being
released.  Thus the adrenal glands are not stimulated, so they stop
overproducing the sex hormones.  Then the ferret gains some weight and
puts on its winter coat.  Even though they both work in a similar manner
Lupron seems to work better and longer.
 
Hope that helps,
Jerry Murray, DVM
PS as for "fish antibiotics" it really depends on what antibiotic it is.
       Some are the same, but some are different.
 
 ------
 
[Sukie note: Forgive me if there winds up being a clump of ferret health
posts.  Steve needed some nursing with influenza and then I got it.
Fortunately, the ferrets didn't get it due to a combination of precautions
and luck, some face masks but more avoidance when needed, many hand
washings, etc.  I am just catching up now.]
[Posted in FML issue 3539]