Understanding Cushing’s disease in dogs
Your veterinarian is correct in that additional blood tests are needed to confirm a diagnosis of Cushing’s disease. If after these tests, your veterinarian has confirmed Cushing’s, there are a couple of different medications that can be used to “shrink” the adrenal glands so that less cortisol is produced. The key is finding just the right amount of medication so that it reduces the production of cortisol, but doesn’t stop it completely.
Long term, your dog should have a decent prognosis, but her life span will possibly be shortened at least a little bit. In my experience, the average dog that is treated properly will live for an additional two to three years after diagnosis. Just be aware that she will have to have periodic blood tests done and remain on medication for the rest of her life.
Q: Our dog has recently been having some issues such as drinking and urinating a lot. She also has been having issues getting around, which we thought was from arthritis, since she is now 10 years old. Our veterinarian ran some blood work on her and she said that she needs to do some additional testing because our dog may have Cushing’s disease. What exactly causes this and what is her long-term prognosis if she does have Cushing’s?
A: Cushing’s disease is typically caused by a benign tumor from the pituitary gland that then stimulates the adrenal glands to secrete excess hormones, mainly cortisol. Cortisol is the body’s natural form of cortisone that it secretes to help with multiple daily functions, especially such things as the flight or fight response that your body has in reaction to fearful or emergency-type situations. So cortisol is normally a good thing, but in excess can be a very bad thing for your dog’s health. It will cause excess drinking and urinating, possible hypertension, and a general loss of muscle mass and strength over time.
Increased Water Consumption and Urination: The most common symptom is increased consumption of water and the resultant increased urination (polyuria/polydipsia). The dogs drink between two and ten times the normal amount of water and the resultant increase in urination follows. This symptom is present in over 85% of all animals with Cushing’s disease. Previously housebroken animals may begin to have accidents because their bladders fill quickly with the overproduction of urine.
Abdominal Enlargement: Abdominal enlargement is a common symptom in up to 80% of the affected dogs. The potbellied appearance is a result of the shifting of fat to the abdominal area and a weakening and wasting of muscle mass in the abdomen.
Hair Loss and Thin Skin: Hair loss and thinning of the skin are also common symptoms in dogs with Cushing’s disease. It is estimated that between 50% and 90% of the affected animals develop these symptoms. Hair loss (alopecia) is one of the most common reasons that owners bring their dog in for evaluation. The hair loss usually starts over the areas of wear such as the elbows and progresses to the flanks and abdomen until eventually only the head and extremities have hair. The skin may also become thin and be easily damaged and slow to heal.
Increased panting, recurrent urinary tract infections, or losses in reproductive ability are other symptoms often noted with this disease.
Cushing’s Disease has two forms
There are two different distinct forms of the disease. There is pituitary dependent hyperadrenocorticism (PDH) and there is an adrenal-based disease.
Pituitary dependent hyperadrenocorticism: PDH involves the oversecretion of ACTH by the pituitary gland. ACTH is a hormone that stimulates the adrenal gland to produce glucocorticoids. The pituitary gland is most likely overproducing ACTH because of a pituitary tumor. The PDH form of the disease is responsible for around 80% of the cases of canine Cushing’s disease.
Adrenal-based hyperadrenocorticism: The adrenal-based form of the disease is usually a result of an adrenal tumor that causes an over secretion of glucocorticoids. Adrenal tumors are responsible for around 20% of the cases of Cushing’s disease. There is also a form of the disease called “iatrogenic” Cushing’s disease that occurs as a result of giving the animal high doses of steroids. In this form of the disease, symptoms of Cushing’s disease will go away once the steroids are discontinued.
Cushing’s disease is a disease that affects middle age to older dogs. The affected animal has a characteristic presentation including increased water consumption and resulting increased urination, increased appetite, hair loss, and a potbellied appearance. There are several diagnostic tests available, as well as several treatments.