Health & Medical

The owner usually mentions it almost as an afterthought. The main reason for the appointment is something else entirely, and then near the door they say, oh, and she has been drinking an awful lot lately, and the water bowl needs filling twice a day now, but she is nine, so I assumed that was just age.

It is often not age. Excessive thirst in an older dog is one of the most useful symptoms in veterinary medicine, and Cushing's disease is one of the conditions it points to.

What is going wrong in the body

Cushing's disease, properly hyperadrenocorticism, means the body is producing far too much cortisol. Cortisol is the stress hormone, and in normal amounts it regulates metabolism, immune response and blood sugar. In chronic excess it slowly dismantles the body: muscle wastes, skin thins, the immune system dulls, and fat redistributes to the abdomen.

There are three routes to it. The most common by far, around 80 to 85 percent of cases, is a small benign tumour on the pituitary gland at the base of the brain, which overproduces the hormone that tells the adrenal glands to make cortisol. Roughly 15 to 20 percent involve a tumour on an adrenal gland itself, which may be benign or malignant. The third form is iatrogenic, caused by long-term steroid medication given for another condition such as severe allergies or immune disease.

Which type matters, because treatment differs considerably.

The signs, and why they get missed

Cushing's develops slowly, usually in dogs over six, and every individual symptom looks like something else.

Increased thirst and urination is typically the first change. Dogs that were reliably clean start asking to go out at night or having accidents. Owners often measure it and are shocked by the volume.

Increased appetite follows, sometimes dramatically. Dogs start stealing food, raiding bins, and behaving as though they are permanently starving. Since older dogs are supposed to slow down, an unusually enthusiastic appetite is easy to read as good health.

Then the physical changes. A pot-bellied appearance develops as abdominal muscles weaken and fat shifts inward, and it can look like weight gain even when the dog is losing muscle over the spine and hind legs. Panting increases, often at rest and at night. Energy drops and the dog tires on walks it used to manage easily.

The skin and coat tell the clearest story. Hair thins symmetrically over the flanks and trunk, usually sparing the head and legs. Skin becomes thin and slack, sometimes with visible blood vessels, and heals badly. Recurrent skin infections and urinary tract infections that keep coming back are classic. Some dogs develop hard calcified plaques in the skin, called calcinosis cutis, which is uncomfortable and quite distinctive.

Certain breeds appear over-represented, including Poodles, Dachshunds, Boston Terriers, Boxers and Beagles, though any dog can develop it.

Getting a diagnosis

There is no single simple test, which frustrates owners who expect a yes or no answer in one visit.

The process usually starts with general bloodwork and urinalysis. A raised alkaline phosphatase liver enzyme, dilute urine and sometimes elevated cholesterol point in the right direction, but they are suggestive rather than conclusive.

Specific testing follows. The low-dose dexamethasone suppression test involves taking a baseline cortisol reading, injecting a small dose of steroid, then measuring cortisol again at four and eight hours. In a normal dog cortisol drops; in a Cushing's dog it does not suppress properly. The ACTH stimulation test measures the adrenal response to a stimulating hormone and is quicker but slightly less sensitive. A urine cortisol to creatinine ratio is a good screening test to rule the disease out, though a positive result needs confirming.

Ultrasound of the abdomen is usually the next step, to look at the adrenal glands. Two symmetrically enlarged glands suggest the pituitary form; one enlarged gland with the other shrunken points to an adrenal tumour.

Testing a dog that is unwell for another reason produces false positives, so vets generally want to treat the obvious problems first and test when the dog is otherwise stable.

Treatment in practice

For the pituitary form, medication is the standard route. Trilostane is the most widely used drug, given daily with food, and it blocks cortisol production. It works well, and most dogs show improvement in thirst and appetite within a few weeks, though coat changes take several months to reverse.

The important part is monitoring. Trilostane requires regular ACTH stimulation tests, initially after ten to fourteen days, then at one month, three months and then every three to six months, with dose adjustments along the way. Too little and symptoms persist. Too much and the dog can swing into cortisol deficiency, which presents as vomiting, diarrhoea, weakness and collapse and is an emergency. Owners need to know that a Cushing's dog that suddenly becomes lethargic and stops eating should not simply be given the next tablet.

For adrenal tumours, surgical removal can be curative if the tumour is benign and has not invaded surrounding vessels. It is major surgery and best done by a specialist. Medication is the alternative where surgery is not appropriate.

For steroid-induced Cushing's, the answer is careful tapering of the steroid under veterinary supervision, never abrupt withdrawal.

What life looks like afterwards

Treated well, dogs with pituitary Cushing's often live two to four years or more with good quality of life, and many die eventually of something unrelated. The disease is managed rather than cured, and that means ongoing cost, ongoing tablets and ongoing tests, which is worth understanding before starting.

Not every dog needs treating immediately. A dog with very mild signs and no complications is sometimes monitored rather than medicated, because the drugs carry their own risks. That is a reasonable conversation to have.

At home, keep water freely available, since restricting it in a Cushing's dog is dangerous. Expect and manage the increased appetite rather than caving to it, because obesity makes everything worse. Watch for skin and urinary infections, which need prompt treatment. And keep a simple diary of water intake, appetite and energy, because those trends are more useful to your vet than any single day's impression.