Cushing's disease, more correctly known as hyperadrenocorticism is caused when the adrenal glands produce too much glucocorticoid, a natural steroid hormone. This overproduction can occur when the adrenal glands themselves are not functioning properly or when the pituitary gland overproduces the compound ACTH or adrenocorticotropic hormone, which in turn overstimulates the adrenal glands to produce the glucocorticiod. The adrenal gland malfunctioning type of Cushing's disease only occurs in about 20% of diagnosed cases with the pituitary overproduction of ACTH making up the rest of the 80%. Regardless of which of the two causes occurs, the general symptoms will be the same although the treatment options will be different.
Cushing's disease can occur in any breed of dog and in both males and females with the same rate of occurrence. There are no breeds that are known to have Cushing's disease more prominent in the breed and as a matter of fact Cushing's disease can occur in horses, cattle, cats and even people. It is not contagious and there is no concern with a dog with Cushing's disease being in contact with other pets or people. Typically Cushing's disease tends to be more common in older dogs and is often diagnosed around the age of seven to ten years of age.
The early signs of Cushing's disease include excessive drinking and frequent urination, often with the dog having many accidents even when fully house-trained. Females are more likely to have bladder and urinary tract infections with these symptoms that may confuse the diagnosis. In addition the dog will be extremely hungry, seeming to be ready and willing to eat at any time of the day. Along with this the dog will begin to become obese, but will take on a particular pot-bellied appearance rather than weight gain uniformly around the body. Part of the pot-bellied appearance is due to the swelling of the liver, which can lead to toxicity problems as the condition worsens. The increase in the steroids in the blood will cause muscle breakdown and the legs will become very thin and spindly in appearance. As the disease progresses the dog will begin to lose hair from the flanks and the body but it will stay long on the legs and the head. This is a very definitive symptom but will only happen once the disease has advanced significantly. The first two symptoms, excessive drinking and urination and a voracious appetite are important indicators of the early stages of Cushing's disease.
The vet will confirm the condition through a variety of blood tests designed to determine the cause of the Cushing's disease. The blood tests will also test for diabetes, toxicity or other conditions that may be occurring at the same time.
Depending on the cause of the condition the treatment will vary. If the symptoms are caused by a tumor in the adrenal gland it can be surgically removed, but the pituitary tumor is typically treated with drug therapies rather than surgery. In many cases these dogs will also have diabetes or other chronic health conditions that will need to be treated at the same time so a holistic treatment plan is required. There are several new medications that are being used very successfully in managing the condition and although they cannot restore full adrenal or pituitary function, they can help to manage the glucocorticoid levels and ACTH levels in the blood.