Cushing's Disease in Dogs and Cats

What is Cushing’s disease?

Cushing’s is an overproduction of a hormone called cortisol, which is used by the body for the fight or flight response. It is also called hyperadrenocorticism.

Cortisol production is governed by both the the pituitary gland located at the base of the brain and the adrenal gland, located in the kidneys. When cortisol levels become too low, the pituitary gland secretes a hormone called ACTH that makes the adrenal gland secrete more cortisol.

High levels of cortisol makes the body quickly use its resources to prepare for the response and is useful in the short term; however,  high cortisol levels in the long term exhausts and debilitates the body.

Who Gets Cushing's

Cushings_disease Cushing’s disease affects both cats and dogs but it is much more common in dogs (there were only 70 cases in cats reported in veterinary literature in the past 15 years). The disease is more manageable in dogs due to their better response to the medicines available for treatment.

Dog breeds most commonly affected are Poodles, Dachshunds, Terriers, German Shepherds and Golden Retrievers.

Types of Cushing’s

Cushing’s is categorized into three groups: Iatrogenic, Pituitary and Adrenal.

  • Iatrogenic Cushing’s is caused by cortisol therapy for other illnesses and can be treated by slowly removing the animal from this therapy. This should always be done slowly because abruptly stopping this drug can result in death.
  • Both Pituitary and Adrenal Cushing’s are caused by a tumor growth in the particular gland. Pituitary Cushing’s makes up 85% of the reported cases and Adrenal Cushing’s make up the remaining 15%. 50% of cases of Adrenal Cushing’s are cancerous.

Symptoms

The symptoms of Cushing’s can be related to so many other diseases and can vary from case to case. The symptoms of Cushing’s are:

  • Excessive urination (Polyuria)
  • Excessive thirst (Polydipsia)
  • Pot bellied or bloated appearance (pendulous)
  • Dermatalogic changes
    • Hair loss
    • Thin or fragile skin
    • Blackheads or clogged pores
    • Increased skin pigment
    • Hard lumps in the skin caused by calcium deposits
  • Enlarged liver
  • Panting § Lethargy
  • Muscle weakness
  • Obesity
  • Muscle atrophy (loss of muscle mass due to weakness)
  • Discontinued heat cycles in intact females
  • Testicular atrophy in intact males
  • Facial nerve paralysis

Treatment

The treatment is directly related to the type of Cushing’s.

  • Pituitary Cushing’s is most commonly treated medically with any of the following medications. Your veterinarian will discuss the best medication for your pet depending on the benefits to your pet, availability and cost.
    • Lysodren (mitotane)
    • Nizoral (ketoconazole)
    • Anipryl (L-Deprenyl, Elderpryl, Selegiline)
    • Trilostane (Vetoryl) – Sold in the UK and not available in the U.S. but can be obtained from another country with special permission from the FDA.
  • Adrenal Cushing’s is a little more difficult in that the vet needs to determine whether the tumor is cancerous or not and if it is, has it spread and to what extent. There are three treatment options for this type of Cushing’s:
    • Medical: Adrenal Cushing’s is medically treated with Lysodren but in higher doses than Pituitary Cushing’s, which increases the risk of side effects. The side effects of the drug can be resolved by removing the pet from therapy and starting up at a lower dose once the side effects have resolved. The average lifespan for a dog undergoing this type of therapy is 16 months.
    • Surgical: surgery is very risky due to the location of the Adrenal Gland (very vascular area) and due to the poor healing ability and high blood pressure caused by the disease. This surgery should be performed by a board certified surgeon and even then the risks may not be avoided. A statistical survey of 63 dogs having surgery for Adrenal tumors resulted in 4 dogs (6%) having inoperable tumors and were put to sleep during surgery. 18 dogs (29%) died in surgery or shortly after from complications. The average lifespan for dogs undergoing this surgery was 3 years.
    • Combination of both treatments.

Related Posts:
To Treat or Not To Treat Cushing's Disease

For more information on this disease talk to your vet or visit the sites below sites:

Information for this post was obtained from Mar Vista Vet, The University of Illinois Teaching Hospital, and Feline Advisory Bureau. Photo courtesy of The University of Tennessee website on Hair Loss