Cushings Disease

The following information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinary physician for confirmation of any diagnosis. Your pets life may depend on it.

Cushing's Disease (Hyperadrenocorticism)

Common clinical signs of hyperadrenocorticism  include :

Pot-bellied appearance - due to increased fat deposition, weakness of the abdominal muscles, and an enlarged liver

Increased thirst - affected dogs drink over 100 ml/kg body weight/day. This is secondary to increased urine losses, and due to a direct effect of glucocorticoids on the thirst centre in the brain. In cats polydipsia is a late sign associated with hyperglycaemia and overt diabetes.

Increased urine loss - passes over 50ml/kg body weight/day . Due to affects of glucocorticoids on antidiuretic hormone. In cats polyuria is a late sign associated with glycosuria and over diabetes.

Increased appetite - direct affect of corticosteroids on the brain

Hair loss - bilaterally symmetrical - particularly along the back, ventral abdomen and the flanks. It  is not itchy and is caused by the effect of corticosteroids which inhibit the anagen phase of hair growth.

Thinning of the skin

Large macules (circular pigmented areas) form on the skin

Calcium deposits in the skin (called calcinosis cutis)

Depression

Generalised muscle weakness - sometimes with obvious muscle wastage (eg temporal muscles) - due to increased protein catabolism caused by the high concentrations of corticosteroids.

Abnormal muscle contractions and rigidity (called myotonia) is sometimes present, creating a stiff gait when walking.

Lethargy and poor exercise tolerance - often mistaken for normal ageing 

Panting at rest

Sometimes behaviour changes - urinating in the house at night due to increased urine production; pacing, head pressing ...neurological signs due to the presence of a large (over 1 cm diameter) brain tumour (uncommon).

Sometimes apparent blindness due to pressure from a large brain tumour (uncommon)

Siezures due to secondary spread of a brain tumour (uncommon)

Atrophy of the testicles occurs in males, and there is inhibition of the oestrus cycle in bitches. These effects are both due to the enhanced feedback mechanism of high cortisol concentrations on the pituitary which inhibits the secretion of gonadotrophic hormones from the pituitary.

Cushing's disease is a disease that affects middle age to older dogs. The affected animal has a characteristic presentation including increased water consumption and resulting increased urination, increased appetite, hair loss, and a potbellied appearance. There are several diagnostic tests available, as well as several treatments. Cushing's disease (hyperadrenocorticism) is a condition that results from the chronic overproduction of too much glucocorcoid  in the body.As a result of the chronically elevated glucocorticoids (steroids), the affected dogs develop a classic combination of dramatic clinical signs and lesions. The disease progresses slowly. A study showed that most dogs had at least one symptom of the disease from one to six years before the disease was diagnosed. Because the symptoms occur so gradually, the owner often attributes the changes to "old age."The most common symptom is increased consumption of water and the resultant increased urination (polyuria/polydipsia). The dogs drink between two and ten times the normal amount of water and the resultant increase in urination follows. This symptom is present in over 85% of all animals with Cushing's disease. Previously housebroken animals may begin to have accidents because their bladders fill quickly with the overproduction of urine. Increase in appetite ,Abdominal enlargement is a common symptom in up to 80% of the affected dogs. The potbellied appearance is a result of the shifting of fat to the abdominal area and a weakening and wasting of muscle mass in the abdomen. Hair loss and thinning of the skin are also common symptoms in dogs with Cushing's disease. It is estimated that between 50% and 90% of the affected animals develop these symptoms. Hair loss (alopecia) is one of the most common reasons that owners bring their dog in for evaluation. The hair loss usually starts over the areas of wear such as the elbows and progresses to the flanks and abdomen until eventually only the head and extremities have hair. The skin may also become thin and be easily damaged and slow to heal.

Increased panting, recurrent urinary tract infections, or losses in reproductive ability are other symptoms often noted with this disease.

There are two different distinct forms of the disease. There is pituitary dependent hyperadrenocorticism (PDH) and there is an adrenal-based disease.

Pituitary dependent hyperadrenocorticism: PDH involves the oversecretion of ACTH by the pituitary gland. ACTH is a hormone that stimulates the adrenal gland to produce glucocorticoids. The pituitary gland is most likely overproducing ACTH because of a pituitary tumor. The PDH form of the disease is responsible for around 80% of the cases of canine Cushing's disease.

Adrenal-based hyperadrenocorticism: The adrenal-based form of the disease is usually a result of an adrenal tumor that causes an oversecretion of glucocorticoids. Adrenal tumors are responsible for around 20% of the cases of Cushing's disease. There is also a form of the disease called "iatrogenic" Cushing's disease that occurs as a result of giving the animal high doses of steroids. In this form of the disease, symptoms of Cushing's disease will go away once the steroids are discontinued.

There are several different tests that can be performed to get a definitive diagnosis of Cushing's disease.

The three most common "screening" tests are the urine cortisol:creatinine ratio, the low dose dexamethasone suppression test, and ultrasound.

Treatment consists of several different options. Depending on the type of disease, surgery can be performed. If an adrenal tumor is identified, then surgical removal may be a viable option. There are several different forms of tumors that can invade the adrenal gland and their treatment will be based on the particular tumor type. There are a few surgeons that have successfully performed surgery to remove the affected pituitary gland in the pituitary form of the disease. However, this is a very specialized procedure and is not commonly performed in the pituitary form of the disease.

Nonsurgical treatment is the most often used treatment for most cases of canine Cushing's disease.

Non surgical treatment is the most often used treatment for most cases of canine Cushing's disease. About 80% of the cases of Cushing's disease in the dog are of the pituitary type, and since both the adrenal and the pituitary type will respond effectively to some of the oral treatments, many veterinarians do not perform the diagnostics necessary to distinguish between the two different forms. There are currently several different oral medications being used to treat canine Cushing's disease.

Lysodren    Ketoconazole     L-deprenyl (Anipryl)          Trilostane

web sites of interest:

http://www.vetinfo.com/dencyclopedia/decushings.html

http://www.marvistavet.com/html/body_cushing_s_disease.html

http://www.thepetcenter.com/gen/cd.html http://www.caninecushings.net/

http://www.provet.co.uk/health/diseases/hyperadrenocorticism.htm

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