When we refer to adrenal disease in the ferret, we almost
always mean HYPER adrenal disease, where adrenal hormone
levels are increased, as opposed to HYPO adrenal disease,
where hormone levels are decreased. This is one of the most
common problems of the domestic ferret. There are numerous
proposed possible reasons including genetic predisposition,
early neutering, nutrition and seasonal light cycle variations.
A large study conducted in Holland demonstrated that ferrets
neutered later in life still had nearly as high an incidence
of adrenal disease as American ferrets, but it occurred
an average of about one year later. Itís most likely this
problem is the result of a combination of factors and not
a single simple one.
Mammals have two adrenal glands, which are typically
located near the kidneys. The normal size of the ferret
adrenal gland is about one-thirtieth the size of the kidney.
In ferrets, the left one lies in an easily accessible area
between the kidney and the vena cava, which is the largest
blood vessel in the rear half of the body. The right adrenal
lies in a much more difficult spot. It is usually attached
to the vena cava itself and is hidden under the central
lobe of the liver. It has traditionally been very difficult
to remove surgically.
The adrenal glands produce many hormones (steroids),
which are essential to life. To date, more than 50 different
steroids have been isolated from the adrenal cortex, the
outer 2/3 portion of the gland. These can be divided into
three main groups: the glucocorticoids (cortisones), the
sex hormones (androstenedione, estradiol, testosterone),
and mineralocorticoids (aldosterone). The inner 1/3 of the
gland, the medulla, produces adrenaline (epinephrine).
In the ferret, most adrenal tumors involve the area of
the adrenal gland that produces sex hormones, although tumors
that produce cortisol or epinephrine do occasionally occur.
For this reason, most of the clinical signs of adrenal disease
are related to either estrogen or testosterone overproduction.
Either of these can occur in either sex. In most cases,
adrenal disease is relatively easy to diagnose, since the
signs are so characteristic.
The most common sign of adrenal disease is hair loss.
The most serious sign in female ferrets is an enlargement
of the vaginal labia, which results from too much estrogen
production. The result, if untreated, can be anemia and
death. High estrogen levels can cause the bone marrow to
stop production of red blood cells. In ferrets, this can
be seen as early as three months from the beginning of labial
enlargement. The most serious sign in male ferrets is difficulty
urinating. This results from enlargement of the prostate
gland due to high hormone levels. If untreated, the swollen
prostate can completely block the flow of urine and death
will result from uremia.
Treatment may be either medical or surgical. While surgical
removal of the affected gland is still the treatment of
choice, a new medical treatment is showing a lot of promise.
Removal of the left adrenal gland is a fairly straightforward
and uncomplicated process and may be performed by anyone
with a little ferret surgery experience. Removal of the
right adrenal gland demands a great deal of confidence and
experience on the part of the surgeon, since the right adrenal
is intimately attached to the largest blood vessel in the
body (vena cava). In our experience, freezing, scraping
or any form of "subtotal" removal of the right gland does
not yield satisfactory results, as the gland usually grows
back within three to six months. The only sure method of
removing the entire gland is to remove the portion of the
vena cava to which the gland is attached, and then suture
the remaining portion of the vessel back together. This
is a procedure with a high degree of difficulty and should
only be attempted by surgeons with a lot of experience.
It is nearly impossible to determine which gland (possibly
both) is involved prior to surgery. The glands are so small
that ultrasound may not give accurate results.
Although there is always some degree of risk associated
with general surgery, we have performed hundreds of adrenal
surgeries, both right and left, with very few complications.
Adding a melatonin implant at the time of surgery when one
adrenal gland is removed may help prevent the remaining
gland from becoming diseased.
Medical options are available for ferrets who cannot
undergo surgery. Medical treatment usually consists of a
melatonin implant, Lupron injection, or a combination of
Melatonin is a hormone that influences the entire endocrine
system. It is thought that this hormone may play a role
in preventing adrenal disease or reversing early adrenal
disease in the same way that manipulation of light cycles
may play a role.
The use of artificial lights to stimulate hair growth
is not a new concept. During the 1930's several studies
were done using artificial light to induce estrus cycles
(heat). During the 1950's the neuropathways of light-induced
estrus were studied. During the 1960's, 70's, and 80's the
hormones and neuropathways involved in reproductive neuroendocrinology
in ferrets were studied. The amount of light per day (photoperiods)
regulates the amount of melatonin. During the spring/summer
months the photoperiod increases (13-15 hours of light per
day) and the melatonin levels decrease. During the fall/winter
months the photoperiod decreases (8-12 hours of light per
day) and the melatonin levels increase. Melatonin directly
and indirectly controls the hypothalamus-pituitary-adrenal/gonadal
axis. Thus the increased melatonin levels (8-12 hours of
light) cause the seasonal weight increase, end the estrus
cycles, and stimulate the hair follicles to grow hair (i.e.
putting on their winter coat). Conversely the decreased
melatonin levels (13-15 hours of light) cause the seasonal
weight loss, start the estrus cycles, and cause the hair
follicles to shed.
Early studies showed that continuous, long-term dosing
of oral melatonin did work in many cases, but only for a
period of eight to ten months. After initial improvement,
ferrets taking oral melatonin had a rebound effect and adrenal
We are now using time-release melatonin implants injected
under the skin to mimic natural hormonal cycles. These implants
are administered every three to six months, and are showing
extremely good results treating adrenal disease that is
not too far advanced. The implants are inexpensive.
Lupron is an estrogen blocker that is used mainly in
treatment of breast cancer in women. It has proved effective
in treating a high percentage of adrenal tumors. It appears
to be as effective against testosterone-producing tumors
as it is against estrogen-producing ones. It is very safe
and has about an 80% efficacy rate. Its main disadvantage
is expense, costing approximately $50 a month and continuing
for the life of the ferret.
Combining the effects of Lupron and melatonin seem to
offer the best possible medical option. In my experience,
adding melatonin to Lupron therapy improves Lupronís effectiveness
There is still much to be learned about ferrets and adrenal
disease. There are currently ongoing studies by practicing
veterinarians all over the U.S. who are combining their
information to produce useful data on surgical techniques
and promising medical treatments. It is an exciting possibility
that the use of melatonin as a preventive in healthy ferrets
will reduce the incidence of adrenal disease as well. It
is of the utmost importance that you seek experienced veterinary
help in deciding on a preventive or a treatment plan for