By Joel Kaye, DVM
Cushing’s disease is the set of symptoms that result from the body being exposed to too much Cortisol over a long period of time. Cortisol is a steroid hormone produced by the adrenal glands which sit above the kidneys. Cortisol is released in times of stress and is one of our “flight or fight” hormones. It causes changes in metabolism to prepare us for physical exertion by mobilizing energy stores and retaining sodium and water. When the body is exposed to this hormone most of the time instead of episodically, it leads to debilitating symptoms.
What are the symptoms of Cushing’s?
There are many symptoms consistent with Cushing’s and considering this is a slow, chronic, insidious disease, many of the signs are dismissed by pet parents as the pet just getting older.
Increased water intake, increased urination, and panting : Pet parents might note the water bowl empties faster than before, or incontinence/urinary accidents when their pet has been trained for years. Their pet may be panting even when the temperature is not warm.
Ravenous Appetite: Pets who never begged for food are now stealing food from the counters, rooting through the garbage, etc…
Potbellied appearance and weakness: A potbellied appearance and weakness results from muscle breakdown and can lead to exercise intolerance and lethargy.
Recurrent skin issues: Recurrent skin issues include hair loss, poor hair growth, thin skin and recurrent infection. There is one syndrome in very chronic stages called calcinosis cutis where calcium is deposited on the skin surface leading to hard-raised plaques on the skin.
Other less obvious or less common symptoms include bladder stones, hypertension, and a rare but debilitating muscle disease called myotonia.
Not every pet with these symptoms has Cushing’s. It is important to determine whether the pet has the disease as well as which type of Cushing’s the pet has.
The 3 types of Cushing’s disease
- Pituitary dependent: This is by far the most common and accounts for about 85% of cases. This is a result of overproduction of a hormone called ACTH which leads to overproduction of cortisol by the adrenal gland. This is usually related to a benign tumor of the pituitary gland called a microadenoma.
- Adrenal dependent: This accounts for about 15% of cases. This is secondary to a tumor of the adrenal gland. Typically this can be found by ultrasound or CT scan.
- Over-use of steroid medications to treat other conditions. Common medications such as prednisone and temaril-p are used long term to treat conditions such as allergies and immune diseases. If not monitored carefully these can lead to something called Iatrogenic Cushing’s disease.
The next step in the diagnosis is specialized blood testing either by an 8-hour blood test called a low dose Dexamethasone suppression test, or a 1 hour ACTH stimulation test. The ACTH stimulation test, though quicker, can miss up to 20% of cases, so I prefer the low dose Dexamethasone test.Once the diagnosis is confirmed, your veterinarian will discuss treatment options. Depending on the severity of clinical signs, no treatment may be the best option.
Cushing’s is typically managed medically with a medication called trilostane. At a few universities, the pituitary form is managed surgically with removal of the pituitary mass.
Most pets with careful monitoring can lead normal healthy lives while being managed for their Cushing’s disease