Hyperadrenocorticism is a slowly progressive disease where the presence of chronically high-levels of cortisol (natural steroid made by the adrenal glands) causes changes in the body. 

A diagnosis of Cushing's must include clinical signs and supporting blood tests.

Cushing's syndrome is caused by an adrenal tumor or a pituitary tumor in 15% and 85% of the patients, respectively.

What is Cushing's syndrome?

• Dr. Harvey Cushing was a neurosurgeon in the early 1900s.  He was an expert on a part of the brain called the pituitary gland, and described a disease in people that was later found to be associated with a problem in humans caused by this gland.  His name stuck with the disease, and it is now also used to describe a very similar problem frequently seen in our canine companions.
• Cushing’s Syndrome (hyperadrenocorticism)
  • Hyperadrenocorticism is a slowly progressive disease where the presence of chronically high-levels of cortisol (natural steroid made by the adrenal glands) causes changes in the body. 
  • There are three main ways this imbalance can occur:
    Pituitary-dependent hyperadrenocorticism (PDH) is caused by a tumor in the pituitary gland secreting excessive amounts of a hormone that  stimulates the adrenal glands to produce cortisol.  A small percentage of these grow in size (called macroadenomas) and will also cause neurological signs.
    A tumor may be present in one of the adrenal glands that is directly making cortisol.
    Dogs (or cats) given chronic steroids (cortisone) can develop symptoms of Cushing’s Syndrome.

Pertinent Anatomy

• The adrenal glands lie on the top pole of the kidneys (arrows in illustration above; kidneys are labeled "K"). In some species they are attached to the outside of the kidneys, yet in other species they are close to the kidneys, but not directly attached to the kidneys.
• The pituitary gland is on the underside of the brain and directly controls the action of the adrenal glands (arrow in photo right).

Clinical Signs

• Most of these dogs are older (6-16 years of age) and smaller breed dogs (under than 40 pounds), but can also be large breeds. 
• Common clinical signs may include
  • Excessive thirst and frequent urinations (they may even begin to have accidents in the house)
  • Ravenous appetite and weight gain
  • Distended abdomen (looks pot-bellied - as seen in photo right)
  • Muscle loss/weakness
  • Lethargy (sleeps all day)
  • Thin skin (may have “blackheads”)
  • Poor hair coat (and hair does not grow back after grooming/shaving)

Diagnosis

• Your veterinarian may be suspicious of Cushing’s Syndrome based on your pet’s history and clinical signs.  Most owners do not notice these changes as they progress slowly and are often attributed to the aging of the pet. 
• As a first step, the entire health of your dog should be evaluated; this includes a full  chemistry profile, complete blood count (CBC), urinalysis and urine culture.  “Cushingoid” dogs usually have elevated liver values, high cholesterol, and changes to their white blood cell numbers. 
• Your veterinarian may also want to take x-rays of your dog’s abdomen or have an abdominal ultrasound performed. 
• If the dog has clinical signs of the disease and consistent changes on their bloodwork, specific tests can now be done to further evaluate them.  These tests on the blood and urine may require your pet to remain at the office for the day. 
• Other serious medical problems can be seen in these dogs including, high blood pressure (in more than 50%), diabetes (due to insulin resistance, kidney disease, pancreatitis, and increased susceptibility to infections. 
  

Treatment

• Treatment of Cushing’s Syndrome depends on the cause of the excess cortisol. 
• If your dog is on any form of steroids, he or she should be weaned off of them and will return to normal over time. 
• Around 85% of dogs with a tumor causing the problem have PDH and 15% have an adrenal tumor. 
• If an adrenal tumor is present, this may be removed surgically, but most of these masses are very difficult to remove and the surgery can be risky. The photo right demonstrates an adrenal tumor that is being removed by one of our surgeons. Our surgeons have extensive experience removing adrenal tumors and their complication rate is relatively low. At the time of surgery the liver should be evaluated for signs of spread. 
• Surgical removal of pituitary tumors is performed on people, but uncommonly in dogs.  Most dogs are treated medically with a drug called Lysodren or mitotane which destroys the adrenal gland tissue.  These dogs must be carefully monitored because some dogs are more sensitive than others to this medication.  If too much of the adrenal glands are destroyed, serious problems can occur without additional medications. 
• A new drug called Trilostane is currently being studied.  This medication decreases the production of cortisol and has fewer side-effects, but is not yet available in the United States. 
• Dogs with large tumors causing neurological signs have limited treatment options and may require radiation therapy.
• Other things to know …...
  • Some of the signs will improve rapidly during treatment (food/water intake), while others may take weeks to months to resolve (with skin/muscle). 

Potential Complications

• Dog's that have Cushing's disease have an increase in the degree of clotting of blood. This could result in the development of a blood clot that lodges in the lungs; the result is severe breathing difficulty or death
• Potential complication of Lysodren treatment is complete destruction of the adrenal glands and a condition called Addison's disease
  • If at any time your pet becomes ill (vomiting, diarrhea, won’t eat, lethargic) he or she should be seen by a veterinarian as soon as possible. 

Prognosis

• Prognosis is good if the owner is watchful and medications are adjusted regularly based on bloodwork results. 
• Many of these older dogs have arthritis or allergy problems which were masked by the cortisol and surface after therapy is initiated.
• Approximately 50% of adrenal tumors are benign and 50% are malignant. If treated early, even malignant adrenal tumors can be cured with surgery.