Cushing's Disease in Dogs

A complete guide on Hyperadrenocorticism for dog owners


This article is written by Pet Circle's qualified veterinarian, Dr Carla Paszkowski, BVSc (Hons)

Has your dog been diagnosed with Cushing's Disease? Or perhaps you are a prospective puppy owner researching your favourite dog breed, but have discovered they are a breed prone to developing Cushing's and want to equip yourself with some knowledge. This guide should provide you with everything you need to know about Cushing's Disease in dogs.

1. What is Cushing's Disease?

2. Which dog breeds are prone to Cushing's Disease?

3. Symptoms of Cushing's Disease

4. Diagnosis of Cushing's Disease

5. Treatment of Cushing's Disease

6. The Best Diet for Cushing's Disease

7. Supplements for Cushing's Disease

What is Cushing's Disease in Dogs?

Cushing's Disease is the common name for Hyperadrenocorticism - a condition in which the adrenal glands (small glands that sit on top of the kidneys) overproduce cortisol in the dog's body. Excess cortisol causes a number of symptoms and affects almost every body system from the kidneys, to the immune system, the skin, and the liver.

What causes Cushing's Disease in Dogs?

In most cases, Cushing's Disease is caused by a benign or malignant tumour in the pituitary gland, or occasionally by a tumour in an adrenal gland. In some cases, Cushing's may be caused by corticosteroid treatment over a long period of time.

The different types of Cushing's Disease

There are three main forms of Cushing's Disease, correlating purely to where the cause of the disease sits anatomically:
- 1. Pituitary Dependent Cushing's. This is the most common form, seen in about 80-90% of dogs with Cushing's. The pituitary gland is a pea sized gland at the base of the brain, and one of its functions is to send signals to the adrenal glands. If the pituitary gland is over active, the otherwise normal adrenal glands will respond to this overstimulation. Usually, a tumour in the pituitary gland causes its hyperactivity - but the tumour itself is oftentimes benign.
- 2. Adrenal Dependent Cushing's. This type of Cushing's is caused by overactive adrenal glands. In most cases, the overactivity is caused by a tumour in an adrenal gland, which causes it to expand and produce excess cortisol. Around 15% of dogs with Cushing's have this type.
- 3. Iatrogenic Cushing's. Iatrogenic typically means 'caused by medication'. This type of Cushing's occurs after a dog has been treated with corticosteroids for a long time.

Dog breeds that are prone to Cushing's Disease

Small breed dogs are particularly prone to Cushing's Disease, however some large breed dogs are affected more than others too. Certain breeds that are prone to developing Cushing's include:

Symptoms of Cushing's Disease

Thinning fur over the torso is a common symptom of Cushing's Disease

Cushing's Disease usually occurs in middle aged and senior dogs. Symptoms typically appear gradually over an extended period of time.

Clinical signs of Cushing's Disease include:
  • Pot-belly (swollen abdomen) appearance
  • Dull or thinning fur, particularly over the torso and abdomen
  • Increased thirst and urination
  • Increased hunger
  • Reduced energy
  • Muscle loss

Diagnosis of Cushing's Disease in dogs

How to tell if your dog has Cushing's Disease

Diagnosis of Cushing's Disease requires a veterinary examination and blood tests. Your veterinarian will be able to inspect your dog's appearance, feel their abdomen, listen to their heart, and perform blood and urine tests.

Blood Tests for Cushing's

While there is no single test that can diagnose 100% of cases, your vet will likely recommend a combination of the following tests:
- Baseline bloodwork (CBC / biochemistry)
- Urinalysis
- ACTH stimulation test - this involves testing the cortisol levels in the blood before and after giving an injection of adrenocorticotropic hormone (ACTH). In a healthy dog, the cortisol level should rise a little. In a dog with Cushing's, the cortisol will start high and rise even higher.
- Low-Dose Dexamethasone Suppression Test - for this, the dog receives an injection of dexamethasone (a steroid). In a healthy dog, the cortisol level will drop because the steroid suppresses adrenal activity. In a dog with Cushing's, the cortisol levels fail to decline.
- High-Dose Dexamethasone Suppression Test
- Urine cortisol to creatinine ratio
- Abdominal ultrasound (this helps observe any changes in the liver and adrenal glands)
- CT or MRI (this can help identify pituitary tumours)

Treatment of Cushing's Disease in dogs

Photo: @windrosestar

The good news is that Cushing's in dogs can be easily treated. However, the type of treatment your dog needs depends on the type of Cushing's Disease your dog has.

As discussed earlier, a pituitary tumour is the most common cause. A dog with pituitary dependent Cushing's can live a normal active life with medication, which moderates steroid production. It is important not to give too much of your dog's Cushing's medication because if steroid levels drop too low, you may push your dog into Addison's Disease (hypoadrenocorticism).

Ongoing care with regular vet check ups will be necessary to monitor your dog's progress and response to medication.

Home Care for a Dog with Cushing's

In addition to giving your dog their medication daily, you will need to monitor your dog's drinking and urination. It's important never to restrict your dog's access to water, and your vet may recommend keeping a water diary to note how much your dog is drinking. It's also important to feed your dog an appropriate food and limit treats and table scraps - read more about this below.

Recommended Diet for Dogs with Cushing's Disease

The ideal diet for a dog with Cushing's disease needs to be:

  • Balanced in line with the Association of American Feed Control Officials (AAFCO) recommendations for adult maintenance - ie, no homemade, raw, or 'all lifestages' diets.
  • Low in fat (<12%) with moderate fibre
  • Contain highly digestible protein
  • Low in Sodium and Chloride - as this can help maintain normal blood pressure

Unlike other conditions such as Kidney disease or Diabetes, a strict Prescription Diet is not required for Cushing's Disease. Most high quality adult diets - particularly those formulated for weight management - will meet the above criteria and keep your Cushingoid dog nourished and healthy.

It is important, however, to strictly limit treats, table scraps, and snacks - particularly those that are high in fat, salt, or sugar. Every tidbit adds up and can contribute to weight gain, which makes Cushing's Disease unpredictable and more difficult to manage.

Top 4 Diets for a Dog with Cushing's Disease

1. Advance Healthy Weight

Available in small, medium, or large breed varieties, this Australian-made dry food is suitable for dogs with Cushing's provided they have no other significant health concerns.
Major callouts: the inclusion of Green Lipped Mussel Powder, which can help keep dull skin nourished, and dried beet pulp for extra fibre.

MACROS (% Dry Matter Basis)1:
Protein: 27.3%
Fat: 9.8% min - 14.2% max
Omega 3 (min): 0.10%
Omega 6 (min): 1.2%
L-Carnitine (min): 55mg/kg
Sodium: not reported
Energy: 345kcal/100g (as fed)

Ingredients: Rice; Chicken Meal; Sorghum; Dried Beet Pulp; Natural Flavour (Chicken); Chicken Fat; Turkey Meal; Sunflower Oil; Vitamins and Minerals; Amino Acids (incl. Arginine, Taurine and Methionine); Salt; Inulin; Antioxidants; Green Lipped Mussel Powder; L-Carnitine

1 Dry matter values calculated using data provided by Advance (8.5% moisture)

2. Hill's Perfect Weight

Available in small, medium, and large breed varieties, this dry food is suitable for dogs with Cushing's provided they have no other significant health concerns.
Major callouts: the inclusion of pea and oat fibre for gut health, coconut oil and flaxseed for healthy skin, and a few extra fruits and veggies for natural vitamins.

MACROS (% Dry Matter Basis)
Protein: 28.7%
Fat: 11.2%
Omega 3: 0.76%
Omega 6: 2.2%
L-Carnitine: 430.4ppm
Sodium: 0.38%
Energy: 323kcal/100g (as fed)

Ingredients: Chicken, Cracked Pearled Barley, Brown Rice, Pea Fiber, Corn Gluten Meal, Chicken Meal, Dried Tomato Pomace, Oat Fiber, Chicken Liver Flavor, Flaxseed, Dried Beet Pulp, Coconut Oil, Pork Flavor, Lactic Acid, Potassium Chloride, L-Lysine, DL-Methionine, Carrots, Iodized Salt, Lipoic Acid, vitamins, Choline Chloride, minerals, Taurine, Mixed Tocopherols for freshness, Natural Flavors, L-Carnitine, Beta-Carotene, Apples, Broccoli, Cranberries, Green Peas.

3. Royal Canin Lightweight Care

Available in small, medium, and large breed varieties, this dry food is suitable for dogs with Cushing's Disease provided they have no other significant health concerns.
Major callouts: the inclusion of fish oil for healthy skin (fish oil is the most bioavailable source of Omegas for cats and dogs compared to vegan alternatives), marine sources of glucosamine for joint health, and psyllium husk for extra fibre.

MACROS (% Dry Matter Basis)1
Protein: 29.8%
Fat: 12.0%
Omega 3: 0.58%
Omega 6: 2.3%
L-Carnitine: 200mg/kg
Sodium: 0.35%
Energy: 314kcal/100g (as fed)

Ingredients: Dehydrated poultry protein, Vegetable fibres, Maize, Wheat, Barley, Maize gluten, Hydrolysed animal proteins, Maize flour, Animal fats, Rice, Beet pulp, Cellulose powder, Vegetable protein isolate, Yeasts and parts thereof, Fish oil, Minerals, Fructo-oligo-saccharides, Psyllium husks and seeds, Soya oil, Hydrolysed yeast (source of manno-oligo-saccharides), Hydrolysed crustaceans (source of glucosamine), Marigold extract (source of lutein), Hydrolysed cartilage (source of chondroitin)

1 Dry matter values calculated using data provided by Royal Canin (9.5% moisture)

4. Pro Plan Weight Loss Sterilised

This Australian-made dry food is suitable for dogs with Cushing's Disease provided they have no other significant health concerns.
Major callouts: the inclusion of fish oil for healthy skin (fish oil is the most bioavailable source of Omegas for cats and dogs compared to vegan alternatives) and beet pulp for extra fibre.

MACROS (% Dry Matter Basis)
Protein: 27%
Fat: 9.0%
Omega 3 (min): 0.2%
Omega 6 (min): 1.5%
L-Carnitine: not reported
Sodium: not reported
Energy: 330kcal/100g

Ingredients: Chicken (dehydrated chicken, chicken); Brewer rice; Whole grain wheat; Oats; Barley; Minerals, Vitamins, Amino acids, Organic acids and Natural flavours; Animal digest; Beet pulp; Dehydrated fish and Fish oil; Animal fat preserved with mixed-tocopherols; Cellulose and Rice hull; Natural Antioxidants.

Supplements for Canine Cushing's Disease?

Supplements are generally not required if you are providing your dog with a balanced adult diet from a vet-recommended brand (like one of the diets recommended above!). However, Cushing's Disease causes elevated levels of cortisol which contributes to higher triglycerides and cholesterol - so there are some supplements that may be beneficial for long term support. These include:

1. Antioxidant therapy consisting of a combination of α-tocopherol, β-carotene, vitamin C, methionine and selenium may be beneficial in lowering circulating blood fats.

2. Fish oil can help lower circulating triglycerides and fats, and may also help improve dull fur or inflamed skin from canine Cushing's disease.

3. Calcium? - Cortisol can increase calcium excretion, however it is not necessary to supplement if your dog's diet is AAFCO forumulated for adult maintenance.

Top Supplements for Canine Cushing's Disease

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