Cushing’s disease or syndrome (Hyperadrenocorticism) is caused when an excessive amount of certain hormones, called corticosteroids, are present in the body. The production of these hormones is regulated by an area in the brain called the pituitary gland and produced by the adrenal glands located near the kidneys. Corticosteroids are necessary for normal body function but the excessive production can lead to a variety of secondary diseases.
There are three major causes of Cushing’s disease:
- Injections or oral administration of steroids (Iatrogenic Cushing’s disease). Although these medications are given for a medical reason, the excess can lead to Cushing’s syndrome.
- A tumor of the adrenal gland. These tumors may be benign or malignant. Benign tumors can often be treated successfully with surgery. If malignant, medical and/or surgical treatment may help for a while, but the prognosis is guarded. Fortunately, this is the least common form of Cushing’s disease.
- A tumor in the pituitary gland. A majority of these tumors are small and primarily cause disease by producing a hormone that subsequently stimulates the adrenal gland to produce too much steroid. When the tumors are small, most of these patients can be treated medically. Occasionally the tumors can become quite large, resulting in abnormal neurological behavior. In these cases, surgery and/or radiation therapy may help, but the prognosis is guarded.
The clinical signs:
The most common clinical signs are increased appetite, water consumption, and urination. A “potbellied” appearance is often seen due to an enlarged liver and weakened muscles. These pets often have a poor hair coat and thin skin. Sometimes, a patient with Cushing’s disease is presented due to lack of hair regrowth after surgery. Some patients will show decreased energy although this is often slow to develop and a subtle change. Some patients also present for panting.
The most common test is an ACTH stimulation blood test. This test will tell us if your dog has Cushing’s disease, but then other tests are needed to determine the type of Cushing’s disease. These are a combination of blood tests and possibly ultrasound, MRI, or CT scanning. Once the specific type of Cushing’s has been determined, then therapy can be instituted.
Depending upon the type of Cushing’s disease present, treatment may vary from slow tapering of steroid therapy for Iatrogenic Cushing’s to using specific drugs to shrink down the over active adrenal glands or surgically removing a tumor.