Hyperadrenocorticism in Dogs

It is commonly found in middle-aged to senior dogs, twelve years or more. Breeds most affected include Boxer, Beagle, Schnauzer, Miniature Poodle, Dachshund, Golden Retriever, Labrador Retriever, German Shepherd, Scottish Terrier and Boston Terrier. Many dogs afflicted are smaller, weighing less than twenty pounds. Many owners will mistakenly overlook this affliction because it’s most tell tale symptoms resemble the natural aging process.

Hyperadrenocorticism in dogs is also commonly known as Cushing's disease. With this affliction, the dog’s pituitary gland is triggered to overproduce cortisol (the stress hormone.)

The most common symptom observed of dogs suffering from hyperadrenocorticism is excessive thirst and urination. Pet owners will note that a once house trained dog is having accidents. The second most observable symptom is a distended pot-bellied appearance of the dog. This is commonly mistaken for a symptom of middle age. Pet owners also often observe increased hunger. Because dogs are natural scavengers and people often reward begging, this symptom is also disregarded. Because decreased hunger is often a clinical symptom of a disease, people often think that a hungry dog does not have a serious condition. Another strange symptom is the disappearance of inflammatory conditions. Again, this is general perceived as  a good thing. The dogs are inadvertently self-medicating their arthritis with cortisol.

• Distended abdomen
• Lethargy
• Muscle weakness and atrophy
• Panting
• Thin skin
• Chronic skin irritation
• Recurrent UTIs
• Heat intolerance
• Skin calcification
• Increased thirst and hunger
• Head pressing
• Circling
• Thinning hair
• Stiff hind legs
• Insomnia
• Darkening of skin
• Hypertension
• Bruising
• Neurological troubles
• Resource guarding
• Trash or counter surfing
• Reluctance to jump
• Calcified skin lumps
• Dull coat

Types 

Pituitary Gland Tumor

This tumor can be benign or malignant. This accounts for by far the largest amount of hyperadrenocorticism diagnosis in dogs. In most cases the tumor is microscopic. On occasion, the tumor is larger and can begin to put pressure on the brain, causing neurological troubles.

Adrenal Gland Tumor

This type of growth can be benign or malignant. It is significantly less common than a pituitary gland tumor.

Iatrogenic Cushing's Disease

Excessive cortisol can be produced from overuse of steroids, particularly for chronic conditions such as allergies. In this case, the dog’s adrenal glands are usually atrophied. However, if the administration of steroids is ceased the dog can resume natural cortisol levels. Unfortunately, the underlying condition requiring the overuse of steroids will resume.

Hyperadrenocorticism is usually caused by a tumor in the pituitary or adrenal gland. Most commonly, hyperadrenocorticism is caused by a benign tumor on the pituitary gland.  It is sometimes caused by the overuse of steroids for another clinical condition.

Diagnosis of  hyperadrenocorticism requires an accurate history and several tests for diagnosis. An ACTH stimulation test and LDDS test are the most common. The former has an approximately 85% accuracy which is higher than the latter. Blood tests may reveal abnormalities such as low blood urea nitrogen and increased ALT. Urinalysis is a common form of analyzing the health of a canine; in this case, the creatinine to cortisol ratio will be studied.

An ultrasound can also be helpful in diagnosing hyperadrenocorticism if a tumor is present. In addition, imaging of the organs and pituitary glands may help confirm the diagnosis.

There are three methods of treating hyperadrenocorticism in dogs. These include surgical, medical, and radiation therapy. The method of treatment depends on the type of Cushing’s disease the dog has.

Tumors or cancers may be treated with radiation or require surgical removal. Studies show that radiation can offer a positive outcome, though medical management for life may be needed as well. Surgery is always a treatment that must be carefully considered; your veterinarian will discuss the complexities of this choice, which may or may not result in resolution of the condition. 

For pituitary hyperadrenocorticism, Lysodren is a medication commonly prescribed. Your dog will need to be carefully monitored on lysodren and communication between owner and veterinarian will need to be well established. Trioleate is commonly prescribed for adrenal hyperadrenocorticism. Again, the dog must be carefully monitored.

There is no real cure for hyperadrenocorticism in dogs. The best prognosis follows the surgical removal of a benign tumor. The removal of malignant tumors has a much less favorable prognosis. Dogs average another two years of life after diagnosis, with or without treatment. Most dogs are diagnosed as seniors so this is considered good prognosis. 

Dogs who undergo medical therapy must remain on medication for life. Often the medications have severe side effects and require careful monitoring.