Cushing’s Disease (otherwise known as hyperadrenocorticism) is a common endocrinopathy causing an increased amount of steroid hormone in your dog. There are two major reasons why this occurs: your dog either has an adrenal tumor or a benign tumor of the pituitary gland (a small gland in the brain). This is commonly a disease for older dogs, but may be diagnosed for younger dogs and, on occasion, cats.
Clinically, you might notice that your dog is very hungry, panting a lot, drinking more than usual, and urinating more frequently. Your dog’s physical appearance will also change, typically presented in a “pot bellied” appearance, thin skin, and potential loss of hair. On an annual exam, abnormalities may show up on blood work that are suggestive of Cushing’s, including elevated liver values and an elevated platelet count. High blood pressure, dilute urine, and a concurrent urinary tract infection may also raise suspicions.
These lab values are just suggestive, and in order to diagnose Cushing’s definitively, a test known as an ACTH stimulation test or a low-dose dexamethasone suppression (LDDS) test need to be conducted. These tests require fasting and that your dog stays in the hospital for 2 to 8 hours respectively. If either of these tests come back positive for Cushing’s disease, an abdominal ultrasound is recommended next. If the disease is due to an adrenal tumor, you will see a very large adrenal gland and one atrophied (small) adrenal gland. If it is due to a pituitary tumor, both adrenal glands will be symmetrically plump.
If your pet has an adrenal tumor, surgery is recommended, though it is a risky procedure that is best performed by a board certified surgeon. Half of adrenal tumors are malignant and half are benign. For this reason, it is important to have a full abdominal ultrasound performed prior to the procedure to check for evidence of metastasis. If there is metastasis or spread of the disease, surgery likely will not be recommended for your pet.
For pituitary-dependent hyperadrenocorticism, the treatment involves giving a medication called Trilostane (Vetoryl). This medication works by blocking the production of cortisone (steroid hormone). However, unlike surgery, this does not cure the underlying cause of the disease, but it does help manage the symptoms that your pet may be experiencing. When your pet is first placed on this medication, they can experience some vomiting or diarrhea. If this does occur, your veterinarian may lower the dose and increase it gradually to help your pet tolerate it better. It is either given once or twice a day and is well tolerated by most dogs. The treatment is lifelong once your pet is diagnosed, and will require diligent monitoring and frequent veterinary follow-up visits.
Cushing’s Disease is a relatively common problem encountered in dogs and can be managed successfully. Most dogs respond to the treatment well and their symptoms can be controlled medically. If surgery is indicated (as in the case of an adrenal tumor), a thorough workup, including imaging, is highly recommended. Dogs can experience a good quality of life with this diagnosis and it carries a favorable long-term prognosis.