Cushing's Disease

Dear Dr. Jody:  Our twelve year old Bichon Frise, “Guinness”, just hasn’t been himself lately.  His coat is getting thinner and he seems to be thirsty all of the time.  He is always panting, even when it isn’t hot outside.  Should we be worried?

While these symptoms are all fairly non-specific when considered alone, together they can indicate a complex syndrome known as Cushing’s disease.  Because this condition is more correctly termed hyperadrenocorticism, it is often abbreviated HAC.  Small breed dogs seem to be more predisposed to HAC than larger dogs. 


Bear with me for a little physiology lesson.  The tiny pituitary gland in the brain is responsible for producing a hormone called ACTH.  ACTH is a messenger that travels to the adrenal glands located next to the kidneys and encourages them to produce more cortisol.  When cortisol is produced in healthy dogs, it travels back to the pituitary gland and tells it to stop secreting the ACTH messenger.  This cyclic mechanism keeps the cortisol levels appropriately balanced. 


In 90% of HAC cases, the pituitary gland is overactive.  It churns out too much ACTH, which tells the adrenal glands to produce excessive quantities of cortisol.  Frustratingly, when these high volumes of cortisol travel back to the pituitary to signal it to cease production of the  ACTH messenger, the pituitary doesn’t pay attention.  It continues working overtime to produce more and more ACTH, and in turn, the adrenal glands cannot stop producing cortisol.


Cortisol is an important substance in the body.  Its duties include assisting in blood sugar control, electrolyte balance, and immune system regulation.  Cortisol is great stuff, but too much of a good thing can be a bad thing.  When cortisol exists in excessive quantities, dogs may experience troubling symptoms such as excessive thirst and urination, panting, increased abdominal fat leading to a pot-bellied appearance, sluggishness, hair loss, thin skin, and an impaired immune system that may predispose the animal to chronic skin, ear, and urinary tract infections.


Simple blood tests and a thorough physical exam by your veterinarian can determine whether the cause of Guinness’ symptoms is HAC.  There are several different treatments available for HAC.  These medications are not without their side effects and limitations, however, so a candid discussion with your veterinarian is key.  While some medications may work in some cases, not all dogs respond quickly or easily to the medications.


Although Cushing’s disease can be quite challenging to manage medically, it is important that you discuss the pros and cons of treatment thoroughly with your veterinarian.  Ignoring the condition is not ideal, as the symptoms can be distressing for your dog.  If you suspect your pet may have Cushing’s disease, please contact your dog’s health care team.