Cushing's syndrome (hyperadrenocorticism) is a chronically debilitating hormone imbalance that can affect many species, humans included; we will be limiting our discussion to dogs and cats, however. Cushing's syndrome, also called Cushing's disease, results from excessive cortisol in the bloodstream and the symptoms all stem from long-term over-exposure to this hormone.

Dogs

There are many clinical signs associated with Cushing’s syndrome (also called hyperadrenocorticism) in dogs. These signs usually come on gradually and, because of this slow onset, these changes are often written off as part of the normal aging process. The following list of common symptoms that an owner might observe in their pet at home is:

• Drinking excessively
• Urinating excessively
• Incontinence 

Thirsty cushings dog

Illustration by Wendy Brooks, DVM

Owners often notice that lately the water bowl must be filled more frequently than in the past. Some dogs are unable to hold their bladder all night and begin crying to go outside during the night when previously this was unnecessary.

Also, urinary tract infections may be detected and true urine leaking may be observed.

How Much Water Consumption is Normal? Each day a dog should drink about one cup of water for each ten pounds of body weight, though this can vary somewhat with environmental temperature and activity level. Dogs that truly have excessive water consumption will consume vastly more than this regularly.

Trashy cushings dog

Illustration by Wendy Brooks, DVM

Increased or even Ravenous Appetite

This symptom often leads dogs to beg incessantly or steal food from the garbage. It is important for an owner not to be fooled by the pet’s apparent good appetite: eating well is not necessarily a sign of normal health.

Pot-bellied Appearance 

Pot bellied cushings

Illustration by Wendy Brooks, DVM

This symptom, present in over 90% of Cushing’s syndrome dogs, results from hormonal redistribution of body fat plus a breakdown of abdominal musculature. Further contributing to the pot belly is an enlarged liver which may bulge a bit especially with weakened abdominal muscles.

Muscle Weakness

Muscle protein is broken down in Cushing’s syndrome. The result may be seen as exercise intolerance, lethargy, reluctance to jump up on furniture or climb stairs.

Skin Disease 

Cushings skin disease

Illustration by Wendy Brooks, DVM

The classical signs of endocrine (hormonal) skin diseases are:

1. Hair loss on the main body sparing the head and legs.
2. Thin, wrinkled skin with poor wound healing.
3. Hair that does not grow back after clipping.
4. Blackheads and darkening of the skin, especially on the abdomen.
5. Persistent or recurring skin infections (especially if the dog is not itchy during times when the skin infection is cleared).

Another condition of the skin that may be observed is called calcinosis cutis, in which calcium deposits occur within the skin. These are raised, hard, almost rock-like areas that can occur almost anywhere on the body.

Aside from the symptoms described above, advanced untreated Cushing's disease puts a dog at risk for the following serious problems:  calcium oxalate bladder stones, diabetes mellitus, and pulmonary thromboembolism.

Cats

Cushings cat

Illustration by Wendy Brooks, DVM

In cats, the clinical features of Cushing’s disease are similar to those in dogs: excess water consumption, muscle wasting, pot-bellied appearance, and thin coat. Cats also can develop a thinning and weakening of the skin to the point of spontaneous tearing or a peculiar curling-in of their ear tips, neither of which is seen in dogs. 

An important difference to note is that while only 10 percent of dogs with Cushing’s disease develop diabetes mellitus, 80 percent of cats with it develop diabetes mellitus. Dogs with Cushing's disease drink excessively because their Cushing's disease makes them do so. Cats with Cushing's disease drink excessively because they are diabetic and their diabetes makes them do so. In fact, most cats are diagnosed with Cushing's disease AFTER their diabetes mellitus has been diagnosed, failed to be regulated and a second disease is being sought to explain poor diabetes control. The 20 percent of cats with Cushing's disease that are not diabetic do not drink excessively.