You may not have heard of it, but Addison’s disease is a serious condition affecting the adrenal glands. Also known as hypoadrenocorticism, it is when the adrenal glands no longer produce sufficient levels of hormones to maintain bodily functions.

Although the condition is rare in dogs, and even less common in cats, the serious and potentially life-threatening nature of the disease means that all pet owners should be aware of the causes, symptoms, and treatment.

What is Addison’s disease?

Addison’s disease is essentially a hormonal disorder, in which the adrenal glands do not produce sufficient amounts of cortisol and aldosterone. The condition is also known as Hypoadrenocorticism.

Cortisol and aldosterone are vital for regulating a wide range of functions in the body, including blood sugar levels, blood pressure, potassium levels, and the metabolism of salt, sugar, and fat. Corticosteroids also regulate an animal’s fight-or-flight response and determine how they cope with stressful situations. Without sufficient cortisol, your pet is no longer able to cope with stress.

Primary Addison’s disease

There are two types of Addison’s disease, primary (typical) and secondary, of which primary is much more common. This is where the adrenal glands themselves stop functioning and no longer produce sufficient levels of hormones. The most common reason for this is an autoimmune disease, where the animal’s own immune system damages the tissue of the adrenal glands. Other reasons the glands may stop functioning properly include tumors, injury or reactions to medications.

Secondary Addison’s disease

The less common type of Addison’s disease is actually a condition of the pituitary gland, which controls the adrenal glands. In secondary Addison’s disease, the pituitary gland no longer produces ACTH (adrenocorticotropin), so the adrenal glands are no longer stimulated to produce cortisol. This secondary form of the disease is often caused by a tumor in the pituitary gland, or if long-term treatment with steroids is suddenly stopped.

Causes of Addison’s disease

Although scientists understand how the disease works, less is known about why exactly a pet develops Addison’s. Although tumors, injury, and reactions to medications can be pinpointed as causes in some cases, these are much less frequent occurrences. The majority of cases come from immune system disorder, for which vets do not know the cause. However, some animals are more at risk, mainly middle-aged cats, female dogs, and dogs of certain breeds.

Dog breeds at particular risk:

• Great Danes
• Standard poodles
• Bearded Collies
• Basset hounds
• Rottweilers
• Saint Bernard
• Portuguese water dogs
• West Highland white terriers
• Soft coated wheaten terriers
• Springer spaniels
• Nova Scotia duck tolling retriever

Symptoms

The signs of Addison’s disease can be hard to pin down. Their non-specific nature means they can easily be confused with symptoms of a number of conditions. Owners may also notice that their pet seems to recover from any ill effects, as the symptoms can come and go – usually appearing more in times of stress.

The most common manifestations of Addison’s disease include:

• Diarréia
• Vômito
• Excessive thirst and urination
• Dehydration
• Lethargy/weakness
• Lack of appetite
• Shaking

Symptoms of acute Addison’s disease will often be similar, but more severe, particularly diarrhea and vomiting. In addition, animals can experience:

• Weakness
• Tremors
• Collapse

Acute Addison’s disease requires immediate treatment, usually hospitalization. If you suspect your dog or cat is suffering from an Addisonian crisis, please contact your vet immediately.

Diagnosing Addison’s disease

Given that the early stages of Addison’s disease can manifest in such non-specific and episodic symptoms, Addison’s can be difficult to diagnose, even for experienced veterinarians. In fact, the disease has been called ‘the great pretender’ or ‘the great imitator’.

Along with a review of your pet’s medical history and a full physical exam, your vet will need to run a series of tests to diagnose your pet. The first will be to rule out other conditions that have similar signs or symptoms. These may include antibody tests to rule out infectious diseases, blood tests to rule out blood-related conditions, and possibly an ECG to rule out underlying heart disease.

Test that may indicate the presence of Addison’s disease include a urinalysis, which determines kidney function; biochemistry profile, which may show high levels of potassium and urea; and a full blood count, which may indicate anemia. If all the signs are pointing towards your pet having Addison’s, your vet will conduct an adrenocorticotropic hormone (ACTH)challenge, which is the definitive test for the disease.

For the ACTH challenge, the animal is injected with a small amount of the adrenocorticotropic hormone, which is naturally produced by the pituitary gland in order to stimulate function in the adrenal glands. If the adrenal glands do not respond to the ACTH by releasing cortisol, then a diagnosis of Addison’s disease can be confirmed.

Tratamento

Unfortunately, Addison’s disease cannot be cured, however, it can be treated. As the condition means that the adrenal glands are no longer producing the correct levels of hormones, the treatment consists of replacing these missing hormones. This usually involves a daily oral hormone supplement or an injection of hormones given every 3-4 weeks.

Over the course of your pet’s life, the dosage of hormone supplements may need to change. Your dog or cat will need regular vet checkups to ensure that their system is getting everything they require. Hormone dosages may also need to be increased in times of stress such as traveling or boarding.

If Addison’s disease develops to an acute stage without treatment or diagnosis, your pet may experience an Addisonian crisis. At this stage, they will need to be hospitalized until they are out of danger. Treatment for an Addisonian crisis involves treating both the cause (the hormone imbalance) and the symptoms: dehydration and shock. Along with cortisol, your dog or cat will receive intravenous fluids containing glucose and electrolytes.

Prognosis

Once your pet is no longer in danger of an Addisonian crisis and is being properly treated, the prognosis is good. Pets diagnosed with Addison’s disease can live long and healthy lives, even after suffering an Addisonian crisis.

Correct treatment relies on a dedicated owner who will make sure that the hormone supplements are always given on time. If your pet has been diagnosed with Addison’s disease, you will also need to be prepared for the additional vet visits that the condition requires to check on hormone levels and any subsequent risks of acute Addison’s disease.