What is Cushing’s Disease?
Cushing’s Disease is a condition in which the hormone cortisol is in an overabundance in a canine’s body. Cortisol is produced in the endocrine system, and typically, cortisol is used to regulate the immune system and fight the effects of stress on the body. At normal levels, cortisol is a necessary and helpful hormone. However, when a canine has Cushing’s disease, the level of cortisol in the body is often quite high, and this factor can result in fairly significant damage to various parts of the body. Known as hyperadrenocorticism, the benign tumor that causes Cushing’s Disease is situated on the pituitary gland. It should be noted that although this tumor is normally benign, there are rare instances of this tumor being malignant. Between 60 – 85 percent of all cases of Cushing’s Disease can be attributed to a condition called pituitary-dependent hyperadrenocorticism (PDH).
What are the Symptoms of Cushing’s Disease?
It is often difficult to diagnose Cushing’s Disease using symptoms alone. Some dogs with Cushing’s are asymptomatic; other dogs may show signs of the condition, but the symptoms of Cushing’s are often mistaken for other ailments. In fact, there is more than one comprehensive test which can tell if a dog is positive for Cushing’s Disease. This adds to the difficulty of diagnosing the condition. Furthermore, although the following list of symptoms is comprehensive, not all of the signs may not be apparent in all dogs with the condition.
Symptoms of Cushing’s Disease include:
-Infertility
-Urinating during the night or otherwise having accidents
-Fat pads on the neck and shoulders
-Hard, white scaly patches on the skin
-Increased thirst
-Muscle weakness
-Bruising
-Increased hunger
-Thin skin
-Increased panting
-Darkening of the skin
-Pot-bellied abdomen
-Lack of energy
-Loss of hair
Cushing’s Disease may be difficult to diagnose, but it is not impossible. Remember, many of the symptoms of Cushing’s Disease mimic other conditions, so the veterinarian may have to rule out other illnesses before ensuring that Cushing’s is truly the condition that a dog is suffering from. The veterinarian will begin by reviewing the dog’s medical history, then order a battery of tests. The first tests are generally the basic laboratory tests any dog would be subject to, the basic blood chemistry profile. A CBC or Complete Blood Count will be ordered as well. The kidneys and the digestive system is also subject to being tested at this point; the veterinarian will order a fecal examination as well as a urinalysis. Once the results from these tests are revealed, the veterinarian can narrow down and run a second battery of tests that will help to pinpoint if Cushing’s Disease is the accurate diagnosis.The first test that can definitively diagnose Cushing’s Disease is a urine cortisol – creatinine ratio test. A high urine cortisol to creatinine ratio result will cause your vet to call for further Cushing’s Disease tests. However, if the urine cortisol to creatinine ratio is normal, the vet will then rule out Cushing’s.
The second test that veterinarians order once a dog shows a high urine cortisol to creatinine ratio is a Low-Dose Dexamethosone Suppression Test. This test is conducted by taking the canine patient’s blood sample and then injecting dexamethasone into the sample. At four hours, the amount of cortisol in the blood is tested; levels are also tested at eight hours. A dog with Cushing’s Disease will see the levels increase over time.
It must be noted that there is no one definitive test to diagnose Cushing’s Disease. If the previous diagnostic tests do not definitively point out Cushing’s Disease, then the veterinarian may order other tests including: an ACTH stimulation test, an abdominal ultrasound, and chest x-rays. Again, most vets will have to rule out other conditions just to insure that Cushing’s is the correct diagnosis.
What are the Two Types of Cushing’s Disease?
There are two types of Cushing’s Disease; one is adrenal-dependent, and the other is pituitary-dependent. The adrenal-dependent form of Cushing’s Disease occurs when the excess cortisol is the result of a tumor situated on the adrenal glands. The pituitary-dependent form of Cushing’s is caused when a tumor is pressing on the pituitary gland, causing it to produce more cortisol than normal. Each of these forms is treated differently.
What are the Treatments for Cushing’s Disease?
It should be noted that the adrenal-dependent form of Cushing’s Disease can be cured if the tumor pressing on the adrenal gland(s) can be surgically removed. At the same time, the adrenal tumor may have spread – making surgery more complicated – and preventing complete reversal of the condition. In fact, some veterinarians are reluctant to perform the surgery even without these risks present because the surgery in itself is quite complex. If this is the case, then the vet will simply prescribe medications to manage the disease.
Cushing’s typically has no cure, especially if it is pituitary-dependent. However, the disease can be successfully managed with medication. An FDA-approved medication is the only one currently on the market that is indicated for treating both pituitary-dependent and adrenal-dependent Cushing’s Disease. Vetoryl (trilostane) was approved for this use in 2008. However, there is a slight drawback – Vetoryl cannot be given to dogs that also have issues with kidney or liver disease, are pregnant, or dogs that take certain heart ailment medications. Anipryl (selegiline) is another FDA-approved medication that is used to treat dogs with Cushing’s Disease, but this drug is only meant to treat dogs whose condition is caused by the pituitary-dependent form of the condition. Some vets will prescribe the human chemotherapy medication Lysodren (mitotane) to treat Cushing’s Disease caused by the adrenal-dependent form of the condition. Note that the prescription of this medication is known to have severe side effects, and it must be carefully monitored by both you and your veterinarian.
Is My Dog at Risk?
While any dog can develop a tumor on its adrenal or pituitary glands, resulting in the development of Cushing’s Disease, there are three breeds consistently associated with the condition: the Dachshund, various Terrier breeds, and the Poodle (as well as variations – the Miniature, the Toy, and the Standard). However, there are other breeds that have experienced a higher incidence rate than normal – Beagles, Boxers, German Shepherd, Labrador Retriever, American Eskimo Dogs, Australian Shepherd, Maltese, and the Cocker Spaniel.
The best way to determine your dog’s risk is to note any changes in panting, thirst, and urination habits, particularly if your middle-aged or older dog is beginning to have accidents regularly.