What causes Cushing’s Disease to Occur in Dogs?

There are several different causes of Cushing’s disease in dogs. The most common one has to do with a tumor developing in the pituitary gland. As a result the body produces too much ACTH and it ignores the response from the adrenal to stop doing so. More than half of all pituitary tumors are smaller than three millimeters in diameter. However, they are able to keep the production of both ACTH and Cortisol going. More than 85% of dogs that are diagnosed with Cushing’s disease have a pituitary tumor that is responsible for the problem.

Approximately 15% of such tumors are larger in size, and the can prove to be more of a challenge. Those that are more than one centimeter in diameter are called Macroadenomas. They can create a variety of problems for your dog because they apply pressure on the tissues and nerves found in the brain. As a result your dog may have problems with vision or even go blind. Seizures and other neurological problems can result as well.

It isn’t always easy enough to diagnose what is going on though, even for a well trained veterinarian. That is because these symptoms are reflective of so many other common problems that older dogs often experience. Various types of testing will have to take place in order to determine what the underlying causes are for your dog. Now that more veterinarians and owner’s are aware of this problem though they can look at other alternatives rather than just taking the situation at face value.

When an adrenal tumor is responsible, it is allowing the body to product too much Cortisol. The statistics are half and half when it comes to these types of tumors being either benign or malignant. The scary part is that if they aren’t diagnosed early they will move aggressively. Many adrenal tumors are able to affect the liver and lungs before they are properly diagnosed. The messages that should be sent from the pituitary to the adrenal glands aren’t interpreted correctly. As a result more and more Cortisol is produced even though the brain knows it should be.

When this type of scenario is taking place, there is one adrenal gland that is larger than the other. This will be the one containing the tumor and you will find that the other one is very small instead of a normal size. In a healthy dog both of the adrenal glands should be the same size. Approximately 15% of dogs with Cushing’s disease are diagnosed due to this type of finding.

Sometimes the disease can be brought on due to the dog being given too much of an external Glucocorticoid. This is a common type of medication given by veterinarians for dogs that suffer from extreme allergies. This is why it so important for your veterinarian to continually monitor the overall health of your dog when such ongoing medications are being used. You will find that the pituitary and adrenal glands strive to get things back in balance. They do so by cutting back on the amounts of ACTH and Cortisol that they produce. Yet that is no match when you continue to give your dog the Glucocorticoid.

Should your dog need to take a type of steroid such as Prednisone, your veterinarian should taper the doses or only offer them every other day. You will find that dog’s exhibiting this type of Cushing’s disease have very small adrenal glands. The good news is that if this disease is triggered due to the medications they are given, it can be cured. Your veterinarian will need to slowly cut back the amount of steroids until the adrenals are able to function normally again.

It is a known fact that dog’s are more susceptible to the development of tumors as they get older. That is why Cushing’s disease is so commonly associated with older dogs but it can be found in those that are middle age as well. The average age of dog’s diagnosed with it is 10 years. There is conflicting information when it comes to the statistics though as some say females are more susceptible while others say it is about 50/50. It is believed that those spayed or neutered do have a higher risk though.

Every breed of dog has been linked to known cases of Cushing’s disease. However, there are some breeds that seem to have a genetic predisposition to it though. They include the Poodle, Yorkshire Terrier, Beagle, Boston Terrier, German Shepherd, Dachshund, Boxer, Golden Retriever, and Scottish Terrier. Smaller breeds of dogs account for approximately 75% of all cases of Cushing’s disease. This includes all breeds of dogs that are less than 44 pounds in weight.