Ferret Adrenal Disease
Adrenal disease is a common syndrome, usually affecting middle aged to older ferrets (four to seven years old). Ferret adrenal gland disease typically results in an overproduction of sex hormones. The most common cause is hyperplasia (excessive growth) of the adrenal gland(s), but tumors, both malignant and benign can be the cause as well. Metastasis (spread outside of the immediate area) of adrenal tumors is uncommon, however, some adrenal tumors can be locally invasive, 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 first 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) and as a result blood levels of LH are high. 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 some may have very dry, itchy skin. As well, despite being neutered or spayed, affected ferrets may return to behaviors typical of an animal that is sexually 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.
Loss of hair Intense itchiness resulting in skin lesions
Swollen vulva in females
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 and can identify which adrenal gland, right or left, is affected prior to surgery. The importance of knowing this is explained below.
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. Removal of the left adrenal gland is technically less demanding as it is usually not attached to vital structures. The right adrenal gland lies very close to a major blood vessel (vena cava), which makes typical surgical removal challenging and many times tumor cells can be left behind. In order to more successfully remove all of the diseased right adrenal gland, some veterinarians advocate a 2-surgery technique where the first surgery uses a device (ameroid ring) to partially constrict the vena cava just behind the diseased adrenal gland. The ferret is surgically closed and 1-3 months later a second surgery is performed to remove the diseased right adrenal. In that 1-3 month time span new blood supply develops around the vena cava and by-passes the adrenal gland. During the second surgery the right adrenal gland can then be removed along with any attached vena cava, as the new blood supply formed since the first surgery allows for complete removal. Since adrenal glands are important in regulating a number of vital body functions, ferrets that have both right and left 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.
Image 1 Image 2
These images show what an enlarged adrenal gland can look like at the time of surgical removal (Image 1 black arrow , image 2 white arrow). Note the large vena cava (black arrow) intimately associated with the right adrenal gland, making its removal a surgical challenge.
There are several medical treatments available for ferrets that are not good surgical candidates. None of them cure the disease itself and their effectiveness will vary. However, in most cases clinical signs can often be completely eliminated and the ferret can resume a good quality of life. The most commonly used and most 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 repeated if and when signs recur. Many exotics veterinarians advocate monthly Lupron treatment for the rest of the ferret’s life as the best way of suppressing disease recurrence. Another drug used to treat the clinical signs associated with adrenal disease is melatonin. A new 90 day slow-release injectable product is now available. Due to the size of the needle associated with this melatonin slow-release pellet the ferret may need to be briefly anesthetized when it is given.
Can adrenal disease be prevented? Newer research has shown that giving Lupron injections once yearly during the ferret’s natural breeding season (end of December/early February) may prevent the onset of adrenal disease as the ferret matures. Ongoing research will determine if this anuual Lupron administration will work in preventing this common disease.
