Could you please tell me about Cushing’s disease in a mixed breed that is approximately 10 years old. What is the cause and is it curable?
Cushing’s disease is a complex and insidious disease that develops as a result of the body overproducing the stress hormone cortisol. This hormone is naturally produced in response to stressful situations and to help maintain delicate hormonal balances. Most cases involve a benign growth in the pituitary gland located at the base of brain, which over-secretes a signal to the adrenal glands to produce cortisol.
The effects of the extra hormone lead to the symptoms of the disease, including increases in thirst and urinations, poor skin and haircoat, panting, increased appetite and weight gain. This hormone also suppresses the immune system, which leads to recurring infections. Over time an enlarged liver can develop and the body may lose its sensitivity to insulin, eventually causing diabetes. In less than 10 percent of cases, an aggressive tumor on the adrenal glands may be the culprit.
These symptoms would lead your veterinarian to run blood tests and possibly perform an ultrasound of the adrenal glands to determine if Cushing’s disease is truly present. Unfortunately, many other conditions can mimic Cushing’s and more involved testing is needed to eliminate other causes.
Once an accurate diagnosis is reached, two common treatments are used to control the symptoms. A daily medication called trilostane blocks the body’s ability to make the hormone. Lysodren is another medication that actually wipes out the cells over the outer layer of the adrenal gland, so the body can’t respond to excess signal produced by the brain. Both medications have serious side effects and treatment needs to be monitored closely. For this reason, the medicines should never be started if an exact diagnosis of Cushing’s disease has not been reached. The initial management period may have problems and adjustment of the dosage is of usually necessary.
Over time with the disease under control, many of the symptoms will reverse and many dogs have excellent quality of life during treatment. A frequently quoted study is that dogs with Cushing’s disease only live two years on average after diagnosis. However, this is a disease of older dogs and I would offer that it may be a function of being old, rather than sick, so it should be taken with a grain of salt.
You asked about a cure and at this time no such hope exists. The best you can hope for is good quality of life through control of the symptoms. In people, advanced surgical options do exist for tumors of the pituitary gland, but those options are not widely available in pets.
You did not specifically say your dog was diagnosed, but I assume there may be a suspicion of the disease. Whether or not to treat is a topic of discussion for you and your veterinarian, but in my experience most dogs that are managed properly do very well.