Adrenal Disease in Ferrets
Adrenal disease is a common syndrome, usually affecting middle aged to older ferrets (three to seven years old). In the healthy ferret the adrenal gland produces a number of different hormones that control a variety of body functions from water to electrolyte balance.
In the diseased or overactive ferret adrenal gland there is typically an overproduction of sex hormones. The most common cause is hyperplasia (excessive growth) of the adrenal gland(s), but tumors, both malignant and benign may also be seen. Metastasis (spread outside of the immediate area) of adrenal tumors is uncommon, however, some adrenal tumors can be very invasive locally, and may grow into the blood vessels or internal organs near the tumor’s origin.
Research has shown that adrenal disease occurs as a result of neutering (spay or castration). The exact reason for this is somewhat complex but in simple terms; when the ferret is neutered it no longer produces sex hormones and consequently there is no sex hormone negative feedback to stop production of other hormones in the brain, specifically luteinizing hormone (LH). This excess LH continuously stimulates the adrenal gland and with time results in the cell changes (hyperplasia or tumor cells) associated with ferret adrenal disease. You might ask, “Then why are ferrets neutered?” Ferrets are neutered in order to prevent other serious health problems and because it makes them better, friendlier pets.
The most common symptom of adrenal disease is a symmetrical hair loss, usually starting at or near the base of the tail and progressing toward the head. If left untreated, affected ferrets can look nearly bald, and may have very dry, itchy skin. Despite being neutered or spayed, affected ferrets may return to sexual behaviors typical of an animal that is intact, and may develop aggression toward other ferrets or people. In some cases this behavioral change may be the only sign of adrenal disease. Females with adrenal disease may appear to be in heat, with an enlarged vulva. Male ferrets may have difficulty urinating or develop repeated urinary tract infections due to prostatic enlargement and inflammation. Some ferrets may lose muscle tone and become weak and lethargic. An increased odor and yellowing of the fur coat may also be noticed.
Diagnosis of adrenal disease is often based on medical history and the classic signs of illness. Routine blood tests are typically normal although anemia (decreased red blood cells) may develop in some ferrets. To definitively diagnose adrenal disease the University of Tennessee provides a blood assay that measures the circulating levels of several hormones produced by the adrenal glands. Elevated hormone levels support the clinical diagnosis of adrenal disease. Ultrasound is also a helpful diagnostic tool used to identify an abnormally enlarged adrenal gland. Monitoring the affected ferret for several months via ultrasound has the added benefit of determining which adrenal gland is growing and thereby most likely to be causing the clinical signs.The preferred treatment for adrenal gland tumors or hyperplasia is the surgical removal of the affected gland(s). This is the only treatment that offers a cure for the disease. Blood work should be done prior to surgery to evaluate the ferret’s overall health. Chest x-rays are often recommended, and if there is any concern about the heart, an echocardiogram (ultrasound of the heart) should be done. There are several surgical methods used to remove the abnormal adrenal gland or glands. In addition to conventional resection, cryosurgery, the freezing of tissue with liquid nitrogen, has been advocated as another method of destroying abnormal adrenal tissue. The right adrenal gland lies very close to a major blood vessel (vena cava), which makes typical surgical removal challenging. Since adrenal glands are important in regulating a number of vital body functions, ferrets that have both adrenal glands removed because of disease may require medication following surgery. Blood tests performed several days after surgery can help determine if supplementation is necessary.
There are a variety of medical treatments available for ferrets that are not good surgical candidates, or for those clients that would prefer a medical approach to treatment. Medical therapies will often completely eliminate the clinical signs we associate with ferret adrenal disease, such as the hair loss and dermatitis, but they will not cure the disease itself. Their effectiveness varies with the level and type of hormones being produced by the diseased adrenal gland. As well, it must be kept in mind that medical therapies are limited in suppressing continued adrenal growth and tumor development which may lead to problems later in life. The most commonly used and a very effective drug treatment option is Lupron® (leuprolide acetate) which is given by injection once monthly until clinical signs resolve (usually this occurs within 3 months) and is repeated if and when signs recur.
Another approach is to administer monthly Lupron treatments for the rest of the ferret’s life. Many veterinarians with a special interest in ferrets feel monthly Lupron® administration is the best way to suppress the hormones we associate with adrenal disease and thereby prevent recurrence of clinical signs.
Another drug used to treat the clinical signs associated with adrenal disease is deslorelin acetate. Like Lupron, deslorelin reduces the production of sex hormones by the affected adrenal gland. Deslorelin is provided in a slow-release pellet about the size of a grain of rice which is injected under the skin and slowly releases a hormone suppressing drug to the point where the clinical signs we associate with adrenal disease resolve. This implant, known as Suprelorin®, does take 4 to 6 weeks to reach its maximum effect, but on the plus side its ability to suppress adrenal-associated hormones can last anywhere from 8 – 20 months with one implant treatment. As a result, it is becoming a popular medical option. Due to the size of the needle associated with the Suprelorin® implant the ferret may need to be briefly anesthetized when it is given.
Can adrenal disease be prevented? Newer research has shown that annual insertion of deslorelin (Suprelorin-F) implants in November or December may delay or prevent the onset of adrenal disease as the ferret matures. The implant suppresses the surge of sex hormones that occurs with the ferret’s natural breeding season.