Q: My dog was diagnosed with Cushing’s Syndrome. What is this disease and what can I expect for my dog?
A: Cushing’s syndrome, or hyperadrenocorticism, is a hormone imbalance that occurs in some older dogs. In Cushing’s Syndrome, the adrenal glands secrete excessive amounts of hormones. These small glands near the kidneys produce cortisol, adrenaline, and other “stress” modulators. When produced in large amounts, these hormones can strain multiple body systems.
Frequently early symptoms of Cushing’s Syndrome are mistaken for aging changes by dog owners. Increased thirst, thinning hair coat, pot-bellied appearance, and urinary tract infections can all be the result of Cushing’s Syndrome. Since many veterinarians now recommend regular laboratory screenings for apparently healthy pets, many Cushing’s patients are now diagnosed very early by detecting the elevation of a single liver enzyme.
The actual diagnosis of hyperadrenocorticism can be lengthy and confusing. Generally veterinarians start with a screening urine test called a cortisol:creatinine ratio. If this test is abnormal, the doctor will stimulate the adrenal glands with an injection and measure the resulting cortisol levels. This test is called an ACTH-stimulation test and takes about an hour to perform. About 10-15% of Cushing’s patients will escape diagnosis on this test and need to have a longer test called a low-dose dexamethasone suppression. A few “atypical” patients may need a special test sent to the University of Tennessee veterinary college before they are accurately diagnosed.
Once diagnosed, the veterinarian will want to determine the cause of the disorder. In 85% of dogs, Cushing’s syndrome is caused by a small growth on the pituitary gland near the brain. The tumor secretes hormones that stimulate the adrenal glands. However, the remaining dogs with Cushing’s syndrome actually have a tumor on their adrenal glands. Differentiating laboratory tests or modern imaging techniques are used to establish the cause.
Left untreated many patients develop more serious illnesses. Diabetes, blood clots, high blood pressure, pancreatitis, seizures, liver failure, and kidney failure can all result from Cushing’s Syndrome. These pets also have suppressed immune systems and may suffer from repeated infections. Treatment options may vary depending on the type, but all are aimed at improving quality of life by preventing these ailments.
Benign adrenal tumors may be cured with surgery. Cancerous adrenal tumors have a poor prognosis. The majority of dogs, with a pituitary mass, are successfully treated with oral medications. The type of medication may vary depending upon your dog’s general health and severity of the hormone excess.
Most commonly a drug called trilostane is used to treat Cushing’s disease in dogs. This medication is given daily and requires very careful monitoring. Overtreatment with trilostane can lead to a sudden deficiency of adrenal hormones, a life-threatening condition called iatrogenic hypoadrenocorticism. Alternate drugs, including ketoconazole and selegilene, are sometimes used to treat Cushing’s syndrome when trilostane therapy is unsuccessful or poorly tolerated.
When certain hormones other than cortisol are involved, some patients respond to natural remedies including melatonin and lignans. The bottom line is that there are multiple treatment options that can be successful when used properly and monitored carefully. Your veterinarian will determine the best option for your dog’s specific situation.
Regardless of the type of hormone imbalance or the treatment option selected, early detection improves outcomes. All pets should be examined by a veterinarian every six months, but that it even more important for pets over seven years of age. Veterinarians should perform routine laboratory evaluations as part of wellness examinations, especially on senior pets. By doing so, Cushing’s syndrome and many other diseases can be caught in their earliest stages, preventing unnecessary illness and suffering.