Cushing’s Disease in Dogs; Types and Treatment

Cushing’s disease, also known as Cushing’s syndrome, is a common endocrine disease of middle-aged dogs responsible for a wide variety of symptoms associated with increased secretion of the hormone cortisol from the adrenal glands.

Breeds that are prone to Cushing’s disease include:

• Staffordshire terriers
• Boston terriers
• Yorkshire terriers
• Poodles, especially miniature poodles
• Dachshunds
• Boxers

Diagnosing Cushing’s Disease in Dogs

Diagnosis of Cushing’s syndrome requires sophisticated tests including special blood and urine tests that may require you pet spend the day at your veterinarian’s clinic. Even with these tests, Cushing’s can be difficult to diagnose, especially in the early stages of the disease or if your dog has concurrent medical disorders. An ultrasound examination may also be recommended to aid in the diagnosis of Cushing’s syndrome and determine whether an adrenal gland tumor is present.

Types of Cushing’s Disease in Dogs

Pituitary Gland Tumor 

The tumor of the pituitary gland is the most common cause of Cushing’s disease (about 85% to 90% of cases). The tumor causes the pituitary gland to secrete excess ACTH, a hormone that triggers the adrenal glands to overproduce cortisol. In general, if the adrenal glands’ activity can be controlled by taking prescribed medication, many canines with pituitary Cushing’s can live normally for years. However, in about 15% of cases, the tumor will grow and affect the brain, resulting in neurological symptoms and giving your furry companion a less favorable prognosis.

Treatment

Though pituitary tumors are removed from people fairly regularly, surgical removal in dogs is not common practice. More often than not, pituitary dependent CD is treated with medications that destroy part of the adrenal cortex, so cortisol levels remain normal.

Adrenal Dependent (ADH)

In ADH, excess cortisol is produced due to a tumor on one of the adrenal glands. Just like the tumor cells in the pituitary gland, the adrenal tumor cells do not have an “off switch” and they continuously produce large concentrations of cortisol. The tumors can be either benign or malignant; if the tumor is benign, it can simply be removed to cure the disease. If the tumor is malignant, however, the prognosis is not as simple.

Treatment

Thankfully, this form of Cushing’s Disease is less common, as it requires more complicated treatment. Typically, this type of CD is treated with surgery to remove the tumor on the adrenal glands. Benign tumors may be cured by surgery, though the process itself is complicated.

Latrogenic HAC

Iatrogenic HAC is really common, but not something many owners might consider a disease. Iatrogenic HAC occurs when dogs are given glucocorticoids and start to develop signs of HAC. For example, many dog owners have likely used glucocorticoids to treat allergic skin disease or used steroid eye or ear drops. Glucocorticoids also are used to treat immune-mediated diseases. Diseases such as immune-mediated anemia, and they’re a cornerstone of  treatment for canine lymphoma. However, some dogs can develop signs of HAC because they’re on these types of medications. The adrenal gland actually shuts down cortisol production in cases of iatrogenic HAC since blood cortisol levels are high due to the medication.

Treatment

This form is easily treated by tapering the offending steroid medication until it is no longer administered. However, the original condition that the steroids were treating is likely to come back.