Cushing’s Syndrome
What is Cushing’s Syndrome?
Cushing’s Syndrome (also known as hyperadrenocorticism) is a condition that primarily affects older dogs. It is caused by an overproduction of hormones by the adrenal glands. The most common cause is a small tumor on the pituitary gland that sends signals to the adrenal glands to overproduce hormones. It can also happen secondary to a tumor on one of the adrenal glands. Cushing’s syndrome can also occur due to exposure to exogenous steroids such as oral and topical steroid medications.
Why would my veterinarian suspect my dog has Cushing’s Syndrome?
Dogs with Cushing’s Syndrome may drink more than normal and urinate more than normal. They may also have an increased appetite, thinning hair coat, and a pot-bellied appearance. In addition they may be more prone to skin and urinary tract infections. If your pet has some of these clinical signs your veterinarian may recommend a comprehensive lab work panel and a urinalysis as the next step.
What laboratory results may indicate Cushing’s Syndrome?
Some patients with Cushing’s Syndrome will have elevations in a liver enzyme called Alkaline Phosphatase (ALP) as well as elevations in cholesterol and triglycerides. Patients can also have elevations in white blood cells called neutrophils, decreased levels of another white blood cell called lymphocytes and increased platelet levels. Some patients will also have dilute urine and some will have elevated urine protein levels.
What tests may my veterinarian recommend if they are suspicious my pet has Cushing’s disease?
In addition to a comprehensive lab work panel your veterinarian may also recommend checking blood pressure as many dogs with Cushing’s Syndrome have high blood pressure. To confirm a diagnosis of Cushing’s Syndrome there are additional blood tests that need to be performed, the most common of which is the low dose dexamethasone suppression test. This test requires an initial blood sample after which your pet will be given an injection of dexamethasone and additional blood samples will be drawn 4 and 8 hours after this injection. This test can be used to diagnose Cushing’s disease and in some cases is able to differentiate whether the condition is due to a pituitary tumor or an adrenal tumor. There are some cases in which a different or additional test called an ACTH stimulation test may be recommended. There is also a test called a high dose dexamethasone test that is used in some cases to help determine which type of Cushing’s Syndrome a patient has. Sometimes your veterinarian may recommend an abdominal ultrasound and/or CT scan for additional information, especially if an adrenal gland tumor is suspected.
My dog was diagnosed with Cushing’s Syndrome. Now what?
The recommended treatment will depend on the type of Cushing’s Syndrome your pet has as well as his or her clinical signs and potentially other health factors.
A medication called Trilostane (Vetoryl) can be prescribed to suppress the overproduction of hormones by the adrenal glands. Because this medication can have potential serious side effects it is important to closely follow your veterinarian’s guidance on recheck exams and recheck lab work. If your pet is found to have an adrenal tumor causing Cushing’s Syndrome, surgery to remove the adrenal tumor may be a possibility. This is usually performed by a board certified veterinary surgeon. Some owners and veterinarians choose not to treat patients with Cushing’s Syndrome if they have mild clinical signs or if there are concerns about the risks of treatment to the patient. This is an important conversation to have with your veterinarian.
Can cats get Cushing’s Syndrome?
It is possible for cats to develop Cushing’s Syndrome, but it is much less common than in dogs. Most cats with Cushing’s Syndrome also have diabetes mellitus.
Written by Dr. Lindsey Taylor