Cushing's Disease in Dogs: Signs, Diagnosis and Treatment

At a glance

What it is	A hormone disorder in which the adrenal glands release too much cortisol, often because of a small growth in the pituitary gland
Who's at risk	Mainly middle-aged and older dogs, more often smaller breeds and some terriers and poodles
Main signs	Drinking and weeing more, ravenous appetite, pot belly, heavy panting, thinning coat and thin skin
Contagious?	No
Can it be prevented?	Natural Cushing's can't be prevented; the type caused by long-term steroid medicine can be reduced with careful prescribing

What it is

Cortisol is a natural hormone made by the adrenal glands, two small glands that sit beside the kidneys. In the right amounts it does useful things: it helps the body cope with stress, regulates blood sugar and dampens inflammation. Its release is controlled by the pituitary gland at the base of the brain.

Vets also call Cushing's disease hyperadrenocorticism. There are three main forms:

• Pituitary-dependent Cushing's is by far the most common. A small, usually benign growth in the pituitary gland sends out too much of the signal that tells the adrenal glands to make cortisol.
• Adrenal-dependent Cushing's is caused by a tumour in one of the adrenal glands itself. These tumours can be benign or malignant.
• Iatrogenic Cushing's is caused by long-term or high-dose use of steroid medicines given for other conditions. It usually improves when the steroids are carefully reduced under veterinary guidance.

Over months, too much cortisol affects almost every part of the body. It weakens muscles, thins the skin, shifts fat to the belly, lowers resistance to infection and drives thirst and appetite. Untreated, Cushing's can also raise the risk of other problems, including high blood pressure, diabetes, urinary infections and, rarely, blood clots.

Signs to watch for

Signs build gradually, which is why many owners only realise how much their dog had changed after treatment begins. Common signs include:

• Drinking much more water and needing to wee more often, sometimes with accidents indoors or waking at night to go out
• A big appetite — begging, stealing food or scavenging more than usual
• A rounded, sagging, pot-bellied appearance
• Panting heavily, even when cool and resting
• Thinning hair or hair loss, often evenly on both sides of the body, with the head and legs spared
• Slow regrowth of fur after clipping
• Thin, fragile skin, with blood vessels easy to see on the belly
• Dark patches on the skin, blackheads, or hard white crusty spots
• Recurring skin or urinary infections
• Weakness, tiring easily, or reluctance to jump and climb stairs

If you notice your dog drinking more, our article on dogs drinking too much water explains how to measure it. Many conditions cause increased thirst, so it is always worth a vet check.

When to see a vet

Book an appointment if your dog is drinking or weeing more than usual, has a constant appetite, a changing shape or coat, or is panting more than you would expect. These signs aren't an emergency on their own, but they deserve investigation.

Contact your vet urgently if your dog:

• Suddenly struggles to breathe or collapses
• Becomes weak, wobbly or disoriented
• Is on treatment for Cushing's and starts vomiting, having diarrhoea, refusing food, or becomes very lethargic or weak — this can mean cortisol has fallen too low, which can be dangerous

How vets diagnose it

Diagnosing Cushing's takes several steps, because the signs overlap with other conditions and no single test is perfect.

• Examination and history. Your vet will ask about drinking, appetite and coat, and check blood pressure, skin and body shape.
• Routine blood and urine tests. Certain patterns, such as raised liver enzymes and dilute urine, make Cushing's more likely and help rule out conditions such as diabetes and kidney disease.
• Specific hormone tests. These measure how your dog's adrenal glands respond to particular injections, with blood samples taken over several hours. Your dog may need to spend part of a day at the practice.
• Imaging. An ultrasound scan of the abdomen helps tell pituitary from adrenal disease by looking at the size of both adrenal glands. CT or MRI scans of the brain or abdomen are sometimes used, particularly if surgery is considered.

Stress and other illnesses can affect the results, so your vet may advise waiting until your dog is otherwise well before testing.

Treatment and management

Treatment depends on the type of Cushing's and your dog's overall health.

• Daily medication is the most common approach for pituitary-dependent Cushing's. It reduces how much cortisol the adrenal glands produce. Treatment usually continues for life.
• Regular monitoring. Blood tests are needed after starting medication and at intervals afterwards, to check that cortisol is controlled without falling too low. Your vet will also ask how your dog's thirst, appetite and energy are changing. Doses are adjusted over time.
• Surgery to remove an affected adrenal gland may be an option for adrenal tumours. It is a specialist operation with real risks, but it can be curative.
• Radiation therapy is sometimes used for large pituitary growths, especially if they cause neurological signs.
• Iatrogenic Cushing's is managed by slowly tapering steroid medication. Stopping steroids suddenly can be dangerous, so this must be done under veterinary direction.

Treatment is not always recommended straight away. If a dog has mild signs and no complications, your vet may discuss monitoring instead. The decision balances the effects of the disease against the commitment and side effects of treatment.

Most dogs show improvement in thirst and appetite within weeks of starting treatment, while coat and skin changes can take months to recover.

Living with it

• Give medication consistently, usually with food, as your vet directs.
• Keep a note of your dog's water intake, appetite and energy, especially in the early weeks — it helps your vet judge the dose.
• Know the signs of cortisol falling too low (vomiting, diarrhoea, poor appetite, weakness) and phone your vet straight away if they appear.
• Keep all monitoring appointments, even when your dog seems well.
• Help your dog keep a healthy weight; the pet calculators can help with portion planning.
• Expect more frequent check-ups for skin, urine and blood pressure.

With good control, many dogs with Cushing's enjoy a good quality of life for years.

Prevention

There is no known way to prevent the natural forms of Cushing's disease. For iatrogenic Cushing's, your vet will use the lowest effective dose of steroids for the shortest time possible. Always follow the prescribed plan, and never stop or change steroid treatment without talking to your vet. Noticing the early signs and having them checked helps catch the condition before complications develop.

Breeds more at risk

Any dog can develop Cushing's disease, but it is seen more often in miniature poodles, dachshunds, boxers and several terrier breeds, including the Yorkshire terrier, Staffordshire bull terrier and Boston terrier. Pituitary-dependent disease is more common in smaller dogs, while adrenal tumours make up a larger share of cases in bigger breeds.