Cushing’s Syndrome

Difficult to Diagnose and Treat in Older Cats

Cushings syndrome (also called hyperadrenocorticism) results from overproduction of glucocorticoids – natural cortisone-like substances – by the adrenal glands.

Its a condition not easy to diagnose and even more difficult to treat, says Richard Goldstein, DVM, an internal medicine specialist at the Cornell University Hospital for Animals. The two main causes of Cushings Syndrome are: A small tumor in the pituitary gland secreting excessive amounts of ACTH, a hormone that causes the adrenals to secrete the glucocorticoid, cortisol, or a cortisol-producing tumor in one of the two adrenal glands. A third cause of Cushings-like signs could be long-term medical use of a glucocorticoid.

Signs to consider
Cushings is uncommon in cats and many veterinarians may see only a few cases in their entire careers, says Goldstein. We really have to have a reason to look for it. Usually the first clue is a diagnosis of diabetes mellitus, caused by a decrease in glucose tolerance and insulin-resistance that occurs from the continual, excessive amount of glucocorticoids. The diagnosis of diabetes mellitus is usually straight-forward, notes Goldstein, who is board certified by the American College of Veterinary Internal Medicine. When it is obvious the diabetic cat is not responding appropriately to treatment, the possibility of Cushings syndrome is considered. Among the clinical signs of feline Cushings syndrome is fragile skin, sometimes so fragile that it will rip with the slightest tension and can tear with normal petting or grooming.

Other signs include weakness, lethargy, poor appetite, and poor hair coat. The cat will have an enlarged liver and, even though very thin, will have a pot-bellied appearance due to redistribution of fat to the abdomen and loss of muscle mass. These signs develop slowly over weeks to months. In cats without diabetes, its very difficult to think of diagnosing Cushings.

Diagnostic tools
Another hindrance to diagnosis is the lack of specific abnormalities in routine urine and blood tests – except hyperglycemia and excessive amounts of sugar in the urine, both expected with diabetes. Two tests have been developed specifically for diagnosing Cushings: The low-dose dexamethasone suppression (LDDS) test and the ACTH stimulation test. They arent 100 percent accurate, but theyre the best we have, says Goldstein. A urine cortisol-creatine ratio test could be done as well but often will give a falsely positive result. Ultra-sound is helpful to look at the liver and assess if there are any masses or cancer, and to look for an adrenal tumor.

Successful treatment uncommon
Treatment depends on the origin of the syndrome. Removal of a pituitary micro-tumor is difficult and currently not an option. Radiation treatment of the pituitary tumor has not been effective either since it could take a long time to see clinical improvement, and we usually dont have a long time with these cats. Medications that block the production of cortisol may be prescribed, but Goldstein says, Unfortunately, none of the medications seem to work well long term. The adrenals develop a tolerance for the drugs. If an adrenal tumor is the origin, suppression of cortisol production may be accomplished with drugs, with the above drawbacks.

Ultimately, whatever the origin, the main long-term treatment today is to surgically remove the adrenal glands. But this causes another disease – Addisons disease or hypoadrenalism; in that case, we will need to supplement the cat with the substances the adrenals would normally secrete.

Id say Cushings is a very uncommon disease to begin with and successful treatment is even less common, says Goldstein. Often, by the time Cushings syndrome is diagnosed, a cat is so sick that even with treatment, the prognosis is poor. These are older cats to begin with; they have diabetes. Now to ask a guardian to spend a lot of money on diagnosis, treatment and surgery … its a lot to put the cat through and a lot to ask of a cats person even though we do recommend treatment, because in some cases the cats are cured of the disease, adds Goldstein. Sadly, many Cushings cats die of the condition or the guardian chooses euthanasia. Hopefully, in the coming years, we will improve in early diagnosis and management of cats with Cushings syndrome.