Hyperadrenocorticism, more commonly known as Cushing’s disease, is a disease that affects the adrenal glands of the body. These glands are located near the kidneys and while Cushing’s disease in dogs is quite common, it’s much rarer to see in cats. Dogs usually develop Cushing’s disease when they are six years old or over, although sometimes younger dogs can also acquire the disease.

What is Cushing’s disease?

Cushing’s disease is one that takes on two different forms: pituitary-dependent Cushing’s, and adrenal-dependent Cushing’s.

Pituitary-dependent Cushing’s is the more common of the two and this type of Cushing’s disease occurs when the pituitary gland in the brain overproduces a hormone, which signals to the adrenal glands to create an excessive amount of cortisol. That excess of cortisol leads to a number of problems and symptoms that will require treatment.

Adrenal-dependent Cushing’s is less common than pituitary-dependent Cushing’s and works very differently. With this type of Cushing’s disease, a tumor develops on one of the adrenal glands. When a tumor is present it needs to be surgically removed and also has the possibility of spreading.

An increase of cortisol in the system occurs with both types of Cushing’s disease and that, in addition with the symptoms of the disease, can also suppress the immune system and make the dog more susceptible to bacterial infections. These infections most often take place in the bladder, although dogs will likely not show any signs of infection.

Because of this, cultures must be taken regularly throughout treatment for the disease, to ensure that the dog’s bladder is not infected.

It’s important to note that certain medications given to dogs, such as Prednisone, can have side effects that mimic those of Cushing’s disease. If your dog is taking any medications, it’s important to speak to your vet before testing for Cushing’s disease.

Diagnosing Cushing’s disease

Diagnosing Cushing’s disease is difficult as there’s no test available that will single-handedly pinpoint the disease.

Veterinary care is still a must, as a vet will be able to review the dog’s history, perform a physical exam, and take blood and urine samples. These samples will be sent to a lab where they will be tested for white blood cell counts, an increase in an enzyme of the liver known as ALP, increased blood sugar, and an increase in cholesterol. These signs, when present, will indicate that Cushing’s disease is a possibility, but still will not confirm a diagnosis. In order to do that, more tests must be performed.

Included in those tests will be x-rays, which will be taken to show a possibly enlarged liver. X-rays may also show calcium deposits in one or more of the adrenal glands, which could indicate that an adrenal tumor is present.

Ultrasounds may also be taken and if Cushing’s disease is present, these will show that the adrenal glands have become enlarged. With pituitary-dependent Cushing’s, both adrenal glands will be enlarged while only one will be larger in size if it’s a case of adrenal-dependent Cushing’s. It’s also important to know that while ultrasounds have been proven to be very effective, the adrenal glands cannot always be seen with these types of tests.

Other types of tests that may be taken to determine the type of Cushing’s disease that’s present include urine cortisol/creatinine ratio, low dose dexamethasone suppression test, high dose dexamethasone suppression test, and an ACTH stimulation test.

Treatment for Cushing’s disease

Once a diagnosis has been confirmed, treatment for Cushing’s disease can begin.

Pituitary-dependent Cushing’s disease is quite easy to treat with an easy oral medication that must be taken for the remainder of the dog’s life. The most common medications that are prescribed are Lysodren and Mitotane. These typically need to be administered twice a day for the first week of treatment. This initial treatment is known as the “induction period” and throughout the course of it, dogs can experience some side effects.

For this reason, it’s important that they’re watched closely, especially during this beginning stage. Once the induction period is over, the medication only needs to be given once or twice a week.

When adrenal-dependent Cushing’s is present, the only course of treatment is to have surgery performed to remove the cancerous adrenal gland. Sadly, sometimes the disease is not caught soon enough and by the time it’s known that surgery is required, the cancer has already spread to other parts of the body that cannot be treated with surgery. Hormones may be given before surgery, and although it’s not as effective as it is with pituitary-dependent Cushing’s, oral medication may also be prescribed.

While there is no cure for Cushing’s disease, dogs that suffer from pituitary-dependent Cushing’s will typically recover from the symptoms once treatment has begun and the induction period is over. While some symptoms might disappear with the onslaught of treatment, others may take longer so it’s important to be patient and continue on with treatment. While the dog’s appetite and thirst will usually return to their normal levels within the first few weeks, it could take months for the dog’s fur to start coming back.

Cushing’s disease in dogs can be very serious so it’s important to speak to your vet at the first signs of the disease. Regular appointments and check-ups are also extremely important as it will give your vet baselines to work from when doing blood work, and will also help them notice changes in your dog’s appearance or overall well-being.