Rely on clinical skills to diagnose ferret adrenal disease - DVM
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Rely on clinical skills to diagnose ferret adrenal disease
CASE STUDY


DVM360 MAGAZINE


Clinical signs If ferrets are exhibiting the clinical signs of adrenal disease, then money is better spent on going right into surgery rather than on expensive tests. Surgery is the most effective treatment for adrenal disease and involves the removal of the affected adrenal gland.


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In most cases, and for reasons unknown, the left gland is most often affected. This is fortunate since removal of the left adrenal gland is relatively easy in comparison to the right adrenal gland. The right gland is often attached to the vena cava and removal can be difficult.

Medical treatment of adrenal disease is usually reserved for ferrets that are poor surgical candidates. They may be older ferrets or ferrets with other medical problems that would make surgery high risk. Some people will opt for medical treatment because of the cost of surgery. Drug treatment must be continued for the rest of the ferret's life and in the long run can cost more than surgical correction.




The drugs used most frequently and successfully for the treatment of adrenal disease are Lupron and Melatonin. Neither will cure the disease but only provide a relief of the signs. Gonadotropin release hormone (GnRH) is released by the hypothalamus in a pulsatile manner to stimulate the pituitary gland to release FSH and LH into the bloodstream. It is necessary for normal pituitary function that the hypothalamus release GnRH in brief discontinuous pulses rather than sustained continuous secretion. The pituitary gland can and will rapidly lose its responsiveness to GnRH if exposed for extended intervals of time - become desensitized.

Lupron (leuprolide acetate) is a synthetic version of GnRH. It is more stable than the natural hormone and, therefore, is degraded much more slowly within the body. This is the key to how Lupron works. Once in the bloodstream, Lupron acts at the pituitary gland just as natural GnRH does.

However, since Lupron is administered at a relatively high dosage and isn't degraded easily, the sustained presence of the drug actually causes the pituitary gland to desensitize and, thus, cease production of LH and FSH.

While some ferrets with adrenal disease do well on Lupron, some ferrets may be unresponsive. This scenario could arise if the adrenal gland has become diseased in a way such that the zona reticularis will produce androgens independent of any regulation by FSH and LH.

If this should occur, the adrenal gland would probably continue to hypersecrete androgens even after Lupron therapy has reduced levels of FSH and LH. Since some ferrets do respond well to Lupron, it is often worth trying if the ferret owner is uncomfortable with the idea of surgery as a first remedy.

Also, Lupron therapy is a life-long protocol: the ferret will require regular doses of Lupron to keep the malfunctioning adrenal gland under control. In the long run, this can be more expensive than surgery, which is presumably a one-time procedure.

Monthly injection of Lupron is given at a dosage of 100 mcg/kg in the muscle of the back leg and then increased to 200 mcg/kg if it is adrenal carcinoma or if the ferret does not respond after two injections. Also, one can use Lupron depot once every four months at 2-3 mg/kg every four to six months intramuscularly. The dosage of 2 mg/kg every four months is five times higher than the 100 mcg (0.1 mg)/kg once a month when compared on a monthly basis. Either way, Lupron is an expensive human product.

There are two other GnRH analogs: Zoladex and Synarel. Zoladex (goserelin acetate) is also a long-acting GnRH analog. It comes in a monthly version and a three-month version. The main problem with Zoladex is it comes packaged already in a syringe, so it would be very hard to divide into sterile dosages small enough for ferrets.

This is also an expensive human product. Synarel (nafarelin acetate) is a nasal solution that would have to be given nasally twice a day. It would be extremely hard to divide this into small enough dosages for ferrets and then give it twice a day nasally.

Melatonin is another product that should stop the stimulation to the adrenal glands. Melatonin is a natural hormone that is secreted by the pineal gland. Melatonin is involved in activating (in the spring) and terminating (in the fall) the ferret hypothalamic-pituitary-gonadal axis in response to the seasonal changes in the photoperiod (amount of daylight).

Melatonin inhibits GnRH release, decreases LH and FSH, and ultimately decreases the sex hormone concentrations. Most of the work with melatonin in ferrets was done with intact jills to bring them into heat or to take them out of heat.


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Source: DVM360 MAGAZINE,
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