More correctly referred to as hyperadrenocorticism, canine Cushing’s disease was named for the doctor who first described this syndrome in people. It is a common metabolic disorder of dogs in which the adrenal gland produces too much steroid hormones, especially cortisol.
Symptoms That Point To Canine Cushing’s Disease
Beagles, Boston Terriers, Boxers, Dachshunds, and Toy and Miniature Poodles appear to have an increased risk for the condition. The disease is a progressive one that is slow and insidious and usually occurs around eight to ten years of age. Complications of Cushing’s disease include increased risk of infection, high blood pressure, congestive heart failure, pancreatitis, diabetes, and blood clotting abnormalities.
Symptoms of Cushing’s disease are:
- increased appetite and thirst
- excessive urination
- neurologic signs (pacing, circling, a drunken walk, head pressing, or seizures)
- symmetrical hair loss on their body
- pot-bellied appearance
- wasting/weakening of the leg muscles
- Color changes in the fur and/or the skin
- skin disease (thinning and loss of elasticity, flaky scales, bumpy irregularities, black head pimples)
KINDS OF CUSHING’S DISEASE
There are different forms of the disease. In the pituitary form of Cushing’s, a tiny and otherwise benign tumor causes the pituitary to over-stimulate the adrenal gland. Smaller breed dogs tend to get tumors of the pituitary gland, and more typically develop neurological symptoms.
About 20 percent of Cushing’s disease is the adrenal form, in which cortisol-secreting tumors develop on the adrenal glands themselves. Larger breed dogs are more likely to develop tumors of the adrenal gland.
A third type of the disease results from drug therapies. The overuse of cortisone-type medications, which are often used to control itchy skin conditions, can result in Cushing’s.
DIAGNOSIS AND TREATMENT OF CUSHING’S DISEASE
Blood tests evaluate the adrenal gland function by measuring the amounts of circulating hormones when the dog is at rest, and in response to adrenal gland stimulating and suppressing drugs. About 40 percent of dogs with Cushing’s have an abnormal test result. The dog’s history and physical examination are most important and prompts additional, more specific tests by the veterinarian. Treatment depends on where the tumor is located.
The pituitary form of the disease is treated with oral medication that controls cortisol secretion from the adrenals. Lysodren (Mitotane), also known as o,p’-DDD, is most often prescribed and it works in almost all cases. Typically, Mitotane is given for the rest of the dog’s life, and quickly reverses many of the symptoms within days to weeks.
Ketoconazole (Nizoral) is an alternative drug treatment for dogs that do not respond well to Mitotane. It inhibits adrenal hormone production and is considered less toxic than Mitotane. It is not FDA approved but off-label use in dogs is common and is considered accepted practice.
When the dog has an adrenal tumor, some experts recommend treating with the drug trilostane for several weeks prior to surgery. Surgical removal of the affected gland is the treatment of choice for the adrenal form of Cushing’s. When the tumor is on only one gland, removing that gland cures the disease. In dogs that do not respond well to any medication, both glands may be removed, followed by oral medication to replace the missing hormones.
S-Adenosylmethionine (SAMe) is a nutraceutical antioxidant that may be helpful in Cushing’s patients with liver complications. A commercial S-Adenosylmethionine supplement (Denosyl SD4) has been demonstrated to improve liver function in these pets.
Treatment for Cushing’s disease reverses the symptoms and improves the dog’s quality of life. It helps the dog live an average of 18 months longer. Dogs diagnosed at an earlier age and successfully treated often live for another five to ten years.