Cushing’s Disease in Dogs: Recognising It Early

Hyperadrenocorticism — Cushing’s disease — is an excess of cortisol, the body’s main stress hormone. It develops gradually, usually in middle-aged and older dogs, and the changes are slow enough that owners routinely attribute them to age.

The signs

Individually unremarkable. Together, distinctive.

• Increased thirst and urination. Often the first thing noticed — a dog emptying the water bowl, asking to go out at night, or having accidents
• Increased appetite, sometimes ravenous. Scavenging and bin raiding in a dog who never did
• Pot-bellied appearance, from redistributed fat and weakened abdominal muscles
• Muscle loss, particularly over the back and hindquarters, so a dog looks thin on top and round underneath
• Thinning coat, hair loss on the flanks and trunk, usually symmetrical and not itchy. Hair that does not regrow after clipping
• Thin skin, prominent blood vessels, slow wound healing, blackheads
• Panting, often at rest
• Lethargy, reduced exercise tolerance
• Recurrent skin and urinary infections
• Calcinosis cutis — hard, gritty white plaques in the skin, in advanced cases

If your older dog is drinking noticeably more, that alone is worth a vet visit. It is one of the most useful symptoms in veterinary medicine, and it narrows the possibilities considerably: Cushing’s, kidney disease, diabetes, and pyometra in unspayed bitches.

The two types

Pituitary-dependent (roughly 80 to 85 percent). A small, usually benign tumour in the pituitary gland overproduces ACTH, which drives both adrenal glands to make excess cortisol.

Adrenal-dependent (roughly 15 to 20 percent). A tumour on one adrenal gland producing cortisol directly. Around half are malignant.

Iatrogenic. Caused by long-term steroid medication. Resolves on careful withdrawal — never stop steroids abruptly.

The distinction matters because treatment differs.

Diagnosis

There is no single perfect test, and diagnosing Cushing’s is genuinely more involved than most conditions.

Screening: general bloodwork and urinalysis, which typically show a raised alkaline phosphatase, dilute urine, and often raised cholesterol.

Confirmatory tests:

• ACTH stimulation test — measures the adrenal response to a stimulating injection
• Low-dose dexamethasone suppression test — measures whether cortisol is appropriately suppressed
• Urine cortisol:creatinine ratio — a useful screening test with a high false-positive rate, best used to rule out rather than rule in

Differentiating the type: abdominal ultrasound to look at the adrenal glands, and sometimes further blood testing.

Blood pressure should be measured — hypertension is common and matters.

Tests are influenced by stress and by other illness, which is why vets sometimes repeat them or wait until a concurrent problem has resolved.

Treatment

Pituitary-dependent: medication, usually trilostane, which reduces cortisol production. Given daily, often twice daily, with food.

This requires monitoring — repeat blood tests at intervals to find and maintain the right dose. Do not skip the rechecks; too much medication causes the opposite problem, which is dangerous.

Adrenal-dependent: surgical removal of the affected gland is potentially curative, though it is major surgery. Medication is used where surgery is not appropriate.

Watch for signs of over-treatment — vomiting, diarrhoea, lethargy, loss of appetite, weakness. If these appear, stop the medication and ring your vet the same day. Iatrogenic Addison’s crisis is a genuine risk.

What improves, and when

• Thirst and urination often improve within a few weeks. Usually the first thing owners notice
• Appetite normalises over weeks
• Panting improves
• Coat and skin take three to six months, and regrowth can be patchy at first
• Muscle mass improves slowly with treatment and appropriate exercise
• Pot belly reduces gradually

Living with it

Water must always be available. Never restrict it, even when the drinking is inconvenient. A dog with Cushing’s who cannot drink freely can become dangerously dehydrated.

More toilet opportunities, and washable bedding. Accidents are not disobedience.

Manage the appetite. A Cushing’s dog is genuinely hungry, not greedy.

• Secure bins and worktops
• Feed measured portions in a slow feeder
• Use low-calorie bulk — green beans, courgette
• Split into three or four smaller meals

Skin care. Thin skin bruises and tears easily. Handle gently, keep nails short, watch for infections, and mention any wound to your vet since healing is slower.

Exercise as tolerated, moderate and regular, to help maintain muscle.

Monitor and record. Water intake weekly, weight monthly, appetite, energy, and any skin changes. This is what your vet uses to judge whether the dose is right.

Concurrent problems

Cushing’s dogs frequently have other issues that need managing alongside:

• Urinary tract infections, often without obvious signs. Periodic urine testing is sensible
• Hypertension
• Diabetes, which can coexist and makes both harder to control
• Pancreatitis
• Increased clotting risk

Prognosis

Well-managed pituitary-dependent Cushing’s is compatible with a good quality of life for years. Many dogs are diagnosed at nine or ten and live comfortably well beyond.

The condition itself is rarely what shortens life; the associated problems — infections, hypertension, clotting, diabetes — are. Which is why the monitoring matters as much as the medication.

And it is worth repeating the first point: the most common story is an owner who assumed an older dog drinking more and looking scruffy was simply getting old. If that describes your dog, it is a blood test and a conversation, not an inevitability.