Cushing’s Disease (Hyperadrenocorticism)

Introduction

Cushing’s disease or Hyperadrenocorticism, is a relatively common endocrine based condition in which the body produces excessive amounts of the steroid hormone cortisol. It is named after Dr Harvey Cushing, a famous neurosurgeon who was the first doctor to recognise the condition in people. Cushing’s disease is also seen in dogs, often affecting particular breeds such as Miniature & Toy Poodles, Dachshunds and some of the smaller terrier breeds. The condition can be artificially induced accidentally by steroidal based drugs prescribed to treat skin problems.

The role of cortisol

In healthy animals, cortisol is naturally produced by the two adrenal glands, one of which is located close to the each of the kidneys. This steroid hormone is vital for good health and is involved in some important functions within the body:

Modulating the immune system
Maintenance of blood pressure
Regulating the action of insulin in controlling blood sugar levels
Regulating how the body uses protein, fats and carbohydrates

The amount of cortisol excreted by the adrenal glands is very closely regulated and finely balanced by a hormone produced by the pituitary gland which is located at the base of the brain. Cortisol is mainly produced at times of stress to help the body cope with difficult situations. In Cushing’s disease however, the levels of cortisol in the blood remain high causing a number of symptoms to appear.

What causes Cushing’s Disease

There are two types of Cushing’s disease.

Most cases of Cushing’s disease occur in animals aged 7 or older. Nearly all cases are caused by a tumour in the pituitary gland. This type is termed Pituitary dependant Cushing’s disease and often occurs in certain breeds of dog. The tumour, which is very small and benign, usually causes no symptoms within the brain itself. However, it does cause excessive amounts of a hormone called adrenocorticotropic hormone (ACTH) to be produced which stimulates the adrenal glands to enlarge and excrete large quantities of cortisol.

The other form of Cushing’s disease is called Adrenal dependant Cushing’s disease. This type is caused by a tumour developing in one of the adrenal glands resulting in excessive amounts of cortisol being secreted. There is no breed predilection for this type of Cushing’s disease, although large dog breeds do seem to be more commonly affected.

Artificially induced, reversible Cushing’s disease, can be caused by veterinary administration of steroidal based drugs to treat some common conditions such as allergies, eczema or arthritis. Fortunately the signs of Cushing’s disease usually disappear quite quickly once the drugs are stopped.

Signs & symptoms

In the early stages, the condition can be very hard to detect, particularly as the symptoms and changes linked with the illness appear very slowly, often over many months or even years. To complicate matters, the symptoms can mirror some of the changes associated with old age, which only adds to the difficulty in detecting the problem. The most common symptoms associated with increased levels of cortisol in the blood are:

Increased thirst (polydipsia)
Increased urination (polyuria)
An increase in appetite and weight gain
Loss or thinning of the hair over the flanks without any irritation
Thinning of the skin
Cessation of hair growth
Changes in hair colour and texture
Enlargement of the abdomen caused by fat deposits in the liver

Less common signs include:

Calcium deposits in the skin (Calcinosis cutis)
Excessive bruising
Comedones (blackheads)
Poor or delayed healing
Stretch marks with a purple hue on the abdomen
Cessation of seasons in bitches
Testicular atrophy in dogs
Muscle wasting and subsequent weakness
Difficulty moving
Suppression of the immune system
Repeated infections
Lethargy
Exercise intolerance

Other than the presenting symptoms, your vet may decide to undertake further investigations or tests to confirm the diagnosis. Common blood findings include:

Raised cholesterol levels
Increased levels of liver enzymes
Increased levels of bile acids

There are also specific tests which your vet may perform to assess adrenal function and to further confirm the diagnosis.

ACTH stimulation test
Low dose dexamethasone suppression test
ACTH assay to determine the level of ACTH in the blood

Further investigations using ultrasound, X-rays and CT/MRI scans can be of additional help in establishing a diagnosis.

Treatment

Conventional options

There are a variety of drugs available to treat Cushing’s disease:

Mitotane (Lysodren). This drug works by destroying the parts of the adrenal gland that produce cortisol so less hormone is produced. This medicine also has the advantage that it kills the cells in adrenal tumours. As most cases of Cushing’s disease are caused by a microscopic tumour in the pituitary gland, mitotane does not address the cause of the disease directly, but rather by reducing the amount of cortisol produced as a result of the pituitary tumour. The use and dose of this drug needs careful monitoring by your vet with frequent blood tests to check on your pet’s progress.

Selegilene (Anipryl). This drug works directly on the pituitary gland by reducing the production of ACTH. It has no effect on the adrenal glands directly. It does not work in dogs that have adrenal tumours and works best in dogs with mild to moderate symptoms of the illness.

Trilostane (Vetoryl). This is a much newer drug which inhibits cortisol production by the adrenal glands. It can be used to treat both forms of the illness. Unlike the other drugs it neither destroys adrenal tissue nor decreases ACTH production. Routine blood tests are needed to monitor your pet’s progress to ensure that the disease is under control.

In rare instances, a surgical approach may be needed to remove an adrenal tumour. This would normally be carried out in a specialist centre as the surgery is technically quite difficult to perform. In addition careful monitoring is required post-operatively to ensure a full recovery.

Most animals with Cushing’s disease are elderly and may have other health issues as well. However, if the condition is monitored and managed adequately, many animals will go on to lead a normal life.

How Denes can help

Although we do not have any specific treatments for Cushing’s disease, we are able to offer supportive treatment to enhance the quality of life for those dogs with the illness.

Denes Liver Support (Milk Thistle+) Powder

Blood testing of dogs with Cushing’s disease often reveals raised levels of liver enzymes and bile acids. Both Milk thistle and Dandelion root are herbs which can support liver function and protect the liver from damage. Denes Liver Support (Milk Thistle+) Powder which includes Dandelion root is an ideal supplement to give to all dogs with Cushing’s especially those on conventional medication.

Denes Homeopathic Phosphorus 30c drops

Phosphorus in its homeopathic form will support the liver and may help ease some of the symptoms of Cushing’s, particularly the thirst and urination problems.

Denes Homeopathic Nux vomica 30c drops

Nux vomica will also support the liver and will help generally by clearing the body of toxins.

Denes Arnica 30c drops

We would recommend Arnica for those animals where bruising is a repeated problem due to the Cushing’s causing fragility of the blood vessels in the skin.

Denes Complete Healthcare (All in One+) Powder

This is an ideal general supplement to give in all cases. It is based on Seaweed, Wheatgrass, Barleygrass, Alfalfa and Spinach and provides a rich source of natural vitamins, minerals and trace elements. In addition, Complete Healthcare (All in One+) Powder will help improve the health of the skin and the coat, which is often poor in Cushing’s cases.

Denes Urinary & Skin Support (Greenleaf) Capsules and Denes Respiratory & Skin Support (Garlic Oil) Capsules

Both these herbal remedies will support general health by helping the body to remove toxins and by supporting the immune system respectively. This combination is particularly effective where there is a problem with repeated skin infections.

Other Denes Fact Sheets to read

Homeopathic remedies
Complete Healthcare (All in One+) Powder
Garlic
Nettles (the main active ingredient in Urinary & Skin Support)