Cushing’s Syndrome (Cushing’s Disease)
by Anne Jones RN, BSNE
Cushing’s is considered a disease of older dogs. However, we have reports of Cushing’s occurring in Bichons as young as 6 years of age. The presence of Cushing’s is not a normal sign of aging and can be treated with some success. In Bichons, it appears often to be associated with over or extended use of steroids being used to suppress the symptoms of allergy. However this is NOT the only reason for the presence of Cushing’s disease in Bichons. The disease may be inherited and is considered one of the principle endocrine disorders in the breed. It often occurs concurrent with diabetes and sometimes with pancreatitis.
Signs and symptoms of Cushing’s are numerous and often mimic other disorders, particularly aging. Your dog age 6 years old or older may have any or all of the following: constant panting, lethargy, strange behaviors, excessive thirst and frequent urination, increased appetite with resulting obesity, enlarged abdomen (which may be edema rather than weight gain), thinning of hair, thinning of the skin, susceptibility to skin infections and slow healing, seeking cool surfaces to lie on, erratic sleep habits and restlessness, lethargy and depression, failure to respond to owner in a normal pattern, diarrhea and/or vomiting, darkening of skin – especially on the abdomen, muscle stiffness, muscle weakness – especially of the rear legs, infertility, a skull-like appearance of the head, and/or seizures. Since these signs may appear in other conditions, blood workup by a veterinarian is definitely in order! Do NOT wait for seizures to develop and be prepared to test for diabetes at the same time. Insulin therapy is not always successful in the presence of both Cushing’s and diabetes.
Cushings’s is known as hyperadrenocorticism and it occurs when too much cortisone or glucocorticoid is present in the body. The hormone cortisol maintains normal blood glucose levels and plays a part in the metabolism of fat as well as the working of the vascular and nervous systems. Overproduction affects these systems as well as kidneys and the immune system.
Causes may include adrenal gland tumors, pituitary gland tumors or constant use of steroids – in Bichons used to treat allergy. It is important to determine which of the causes has made the dog sick. A first step is to have your veterinarian examine the dog. He may test for serum alkaline phosphatase, cholesterol, alanine transferase, blood glucose, and urinalysis to check for low specific gravity and high protein levels. CT scans, ultrasound or x-ray examination may be needed. Old tests for Cushing’s that used ACTH were extremely expensive. Today a low dose dexamethasone test may be used. If the dexamethasone does NOT suppress the level of cortisol in the blood, Cushing’s is suspected. A further test may be necessary to determine if the disease is from adrenal gland tumors or pituitary tumors. These tests are rather costly but necessary for diagnosis.
In the case of the dog on daily or frequent doses of steroid treatment, the veterinarian may advise a gradual reduction and finally elimination of the steroid to see if the symptoms abate. This is a judgment that must be made under advice of the veterinarian and the dog must be monitored throughout. Blood tests and other lab work may still be needed to determine if the dog has true Cushing’s. The disease occurs often enough to suspect other causes than steroid use. As mentioned earlier, the disease often occurs with or is followed by the developing of diabetes mellitus.
In recent years, the same drug that is used to treat Cognitive Dysfunction (senility) in dogs is one that is sometimes used to treat Cushing’s. The drug Anipryl (generic name selegiline) works to suppress the pituitary gland and may be effective if the cause is pituitary tumor. Earlier drugs used to treat Cushing’s (Lysodren, ketaconazole, Mitotane) all can have very serious side effects and need close monitoring. These are all being used in severe cases of Cushing’s. Monitoring of food and water intake is necessary to know if and when the drugs are effective (usually within 2 weeks). It is noteworthy that Addison’s disease (hypoadrenocorticism) is rarely seen in Bichons. However it can result when treatment by Lysodren is overdone. Addison’s is an inherited condition in some breeds.
Many veterinarians use a two year estimate for life span following a diagnosis of Cushing’s so you can see need to both treat and to monitor treatment. With the numbers of cases of Cushing’s that are seen in Bichons, this further strengthens the need for breeders to eliminate serious allergies in the breed and to avoid the use of steroids in treating those with allergies. If steroids must be used, try to use a single dose and then switch to antihistamines or to give the prednisone on alternate days rather than daily.
Material obtained from Merck Manual, Your Dog magazine and various medical and veterinary texts.
Dogs, Diet, and Disease: An Owner’s Guide to Diabetes Mellitus, Pancreatitis, Cushing’s Disease, and More by Caroline D. Levin RN