Cushing’s Syndrome: Diagnosis and Treatment

Cushing’s Syndrome: Diagnosis and Treatment
By Dr. Ed Mapes
Stonebridge Animal Hospital

Symptoms of Cushing’s Syndrome in Pets

Increases in thirst (polydipsia), urination (polyuria), and appetite (polyphagia) are symptoms seen in a number of diseases, and one of the most important of those is called Cushing’s Syndrome. This is also called hyperadrenocorticism.

Notice the hair loss and “pot-belly” appearance of this dog with Cushing’s Syndrome.


The signs of Cushing’s are caused by an overproduction of cortisol (cortisone) by the body’s adrenal glands. This excessive cortisol also causes decreased immune response to infection, thinning of the skin, symmetrical hair loss over much of the body, chronic skin infections, decreased activity levels, having a bloated appearance, development of skin pigmentation, and poor wound healing. Pets may become weak, pant excessively, and have muscle tremors as well.

Cortisol is normally produced by the adrenal glands in response to a hormone (ACTH) produced by the pituitary gland in the brain. This production is based on the ever-changing bodily requirement for cortisol, and is strictly regulated by the body.

Different Forms of Cushing’s Syndrome

  • Cushing’s syndrome can be caused by a tumor of the pituitary gland that increases blood levels of ACTH. This stimulates the adrenal glands to overproduce cortisol. This is the most common form of Cushing’s, seen in approximately 85% of cases.
  • The other form of Cushing’s is caused by a benign or malignant tumor of the adrenal gland(s), also resulting in elevated levels of cortisol production that is independent of ACTH control.
  • A third form of Cushing’s (Iatrogenic) is caused by the over-administration of cortisone to animals. This is the reason that I always attempt to avoid using cortisone in treatment regimens, and to limit their use when the drugs are necessary. Differentiation in the cause of a particular case is important because treatment and prognosis of the various types differ.

Diagnosing Cushing’s Syndrome in Pets

Arriving at the correct diagnosis is very important when confronted with a patient exhibiting symptoms of Cushing’s. First we must differentiate this disease from others with similar symptoms. This involves blood testing, urinalysis, and sometimes abdominal radiographs or ultrasound to provide baseline information. When these tests indicate a possible diagnosis of Cushing’s syndrome, separate testing is done to differentiate the type of Cushing’s present to guide us in prescribing the appropriate treatment.

Treating Cushing’s Syndrome in Pets

Two drugs, trilostane (Vetoryl) and mitotane (Lysodren) are used to control ACTH production in the treatment of the pituitary dependent Cushing’s. Treatment begins with the administration of the medication for 10 days, and then a repeat of a blood test is done to confirm control of cortisol and to ensure that the adrenal glands are not “shut down” entirely. Dosages of the medication may be altered or continued based on these test results.

Repeating of this testing is done whenever the patient begins to drink, urinate, or eat excessively. I also prescribe small dosages of cortisone tablets to administer whenever the patient is stressed for any reason because the body requires elevated cortisol levels in those situations.

When an adrenal tumor causes the syndrome, abdominal surgery is required to remove the tumor. Successful resection of a benign tumor can lead to normalization of cortisol levels and a return to normal health. Malignant tumors, even when removed, have the potential to re-occur or to spread to other body tissues, and so have a poorer prognosis.

Treatment of iatrogenic Cushing’s requires the gradual, controlled cessation of the cortisone being given. This must be under continued veterinary guidance to ensure a successful transition and continued treatment of the condition for which the cortisone was prescribed.

Cushing’s syndrome is a serious disease that can lead to other problems in the body such as diabetes insipidus and kidney or liver failure. Pets should be taken to a veterinarian whenever the symptoms discussed earlier arise because early diagnosis and treatment can prevent other problems from arising, which are far more difficult to manage.

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