Cushing’s disease is an excess of cortisol, the body’s stress hormone, most often caused by a small benign tumour affecting the pituitary gland. The classic picture is an older dog drinking and urinating far more, eating ravenously, developing a pot-bellied shape and losing coat. Each sign alone reads as ageing, which is why it goes unrecognised.
The conversation that usually starts it
Almost every diagnosis begins with a passing comment at the end of an appointment. The dog is in for something else entirely, and on the way out the owner mentions that the water bowl needs filling twice a day now, or that there have been a few accidents overnight after years of none.
That detail is worth leading with rather than mentioning as an afterthought. Increased drinking is one of the most useful signals in canine medicine, and it points at a short list of conditions that are all worth finding early.
What cortisol does, and what too much of it does
Cortisol is a normal and necessary hormone. It helps regulate blood sugar, blood pressure, the immune response and the body’s handling of stress. Produced in the adrenal glands, its release is controlled by signals from the pituitary gland at the base of the brain.
In roughly the large majority of cases, a small benign tumour in the pituitary gland sends a continuous signal to produce more cortisol. Less commonly, a tumour in an adrenal gland itself produces cortisol independently. A third form is caused by long-term steroid medication given for another condition, which is important because it is the one form that is reversed by carefully adjusting that treatment rather than by adding new medication. Never stop a prescribed steroid abruptly on your own; that is genuinely dangerous, and any change must be managed by your veterinarian.
Sustained excess cortisol affects almost every system, which is why the sign list is so scattered and so easy to attribute to age.
The signs, and why each one gets excused
- Drinking noticeably more, and urinating more, with accidents overnight in a previously reliable dog
- A ravenous appetite, including scavenging, counter-surfing or stealing food from an old dog who never did
- A pot-bellied or sagging abdomen, caused by muscle weakness and fat redistribution rather than fat alone
- Thinning coat, hair loss on the flanks and body that spares the head and legs, and hair that does not regrow after clipping
- Thin skin, easy bruising, blackheads, recurrent skin infections and slow wound healing
- Panting far more than the weather or activity explains
- Muscle weakness, reluctance on stairs, and a lower exercise tolerance
- Lethargy and reduced interest in walks
- Recurrent urinary tract infections, sometimes without obvious signs
Individually, every one of those is what people expect from an ageing dog. Together they form a recognisable pattern, and it is the combination that should prompt testing. A dog who is drinking more, panting more, hungrier than ever and losing coat is not simply old.
Who it affects
It is predominantly a disease of middle-aged and older dogs. Recognised predispositions include Poodles, Dachshunds, Boston Terriers, Boxers, Beagles and several terrier breeds, though any breed can be affected. Small breeds are more commonly affected by the pituitary form; the adrenal form is seen relatively more often in larger dogs.
Cats develop it far less frequently, and when they do it is often alongside diabetes that is proving difficult to control. Fragile skin that tears easily is a particularly notable feature in affected cats.
Why testing takes more than one visit
This is the part that frustrates owners, so it is worth explaining properly. There is no single quick blood test that gives a yes or no answer.
Screening usually starts with general bloodwork and a urine sample, which often show suggestive changes such as a raised liver enzyme, dilute urine, or evidence of infection. Those findings support the suspicion but do not confirm it.
Confirming the diagnosis requires a dynamic test, meaning blood samples taken at set intervals over several hours, sometimes with a medication given in between. That is why these appointments involve leaving your dog with us for part of a day. Further testing and imaging may then be recommended to distinguish the pituitary form from the adrenal form, because the treatment differs.
Stress and other illnesses can affect the results, so tests are sometimes repeated or timed deliberately. Our diagnostic services carry out each stage, and the interpretation happens in a medical consultation alongside what you have observed at home. Our post on when digestive changes need investigating makes a similar point about not treating a symptom without establishing the cause.
The single most useful thing you can bring is a measurement. For three days, measure how much water goes into the bowl and how much is left. That number is more informative than any impression, and it also gives a baseline to judge treatment against later.
Living with it
Cushing’s disease is managed rather than cured, and with appropriate treatment many dogs feel substantially better and return to a good quality of life. Treatment for the common pituitary form is medication prescribed and closely monitored by your veterinarian, and the monitoring is not optional. The dose is adjusted based on repeat testing, and both undertreatment and overtreatment cause problems, so recheck appointments are the core of managing this well.
Where an adrenal tumour is the cause, surgery may be considered, and that discussion involves our surgical services team along with imaging to assess the tumour first.
Expect improvements in a sequence rather than all at once. Thirst and appetite usually settle within weeks. Skin and coat take months, and coat regrowth is often the last thing to come back, so a dog who is drinking normally but still patchy is generally doing fine.
Report anything new during treatment rather than waiting for the next appointment, particularly vomiting, diarrhoea, weakness, or a dog who suddenly goes off food. Those can indicate the dose needs review, and that is a same-day conversation through our urgent care service.
Ongoing monitoring for older dogs generally, including the bloodwork that first raises this suspicion, is part of our wellness program. Our guide to warning signs every Abbotsford owner should know covers the wider list of changes worth reporting.
Frequently asked questions
Is Cushing’s disease in dogs fatal?
It is a chronic condition that is managed rather than cured, and many dogs live comfortably for years with appropriate treatment and monitoring. Left untreated it causes progressive problems including muscle weakness, skin disease, recurrent infections and an increased risk of other conditions. The outlook depends on the form, the dog’s age and any other illnesses present.
Why does my dog need to stay for several hours of testing?
Because there is no single blood test that confirms it. Diagnosis requires a dynamic test, with samples taken at set intervals over several hours and sometimes a medication given in between, to see how the body responds. Screening bloodwork can raise the suspicion but cannot confirm it, and further testing may be needed to identify which form is present.
My old dog drinks a lot but seems happy. Should I worry?
It is worth investigating. Increased thirst is one of the most useful early signals in canine medicine and points to a short list of conditions, several of which are much easier to manage when caught early. A dog can feel reasonably well while a condition progresses. Measure the water intake over three days and bring that number to an appointment.
Will treatment make my dog’s coat grow back?
Often yes, but slowly. Thirst and appetite usually improve within weeks, while skin and coat changes take months and hair regrowth is typically the last thing to return. Patchy coat several weeks into treatment is normal rather than a sign that treatment is failing, and the more meaningful early markers are drinking and eating.
Can steroid medication cause this?
Yes. Long-term steroid treatment given for another condition can produce the same picture, and this form is addressed by carefully adjusting that medication rather than adding another. Never stop a prescribed steroid suddenly, as that is dangerous. Any change must be planned and supervised by your veterinarian.
Do cats get Cushing’s disease?
Rarely, and when they do it often appears alongside diabetes that is difficult to control despite appropriate treatment. Extremely fragile skin that tears easily is a characteristic feature in affected cats. Because it is uncommon, it is usually considered once more likely explanations have been ruled out.