Addison’s Disease in Dogs

Addison’s disease in dogs is a disorder which is caused by insufficient levels of hormones produced by the adrenal glands. It’s named after Thomas Addison, the British scientist who first discovered the disease.

We’ve put together this guide to tell you all you need to know about Addison’s in dogs, including the symptoms and treatment options currently available. Keep reading to find out more.

What is Addison’s Disease in Dogs?

Addison’s disease is the common name for hypoadrenocorticism, a disease that occurs when there are insufficient levels of some of the hormones produced by two small glands, known as the adrenal glands. These glands are located near the kidneys and are responsible for producing several important hormones.

One of these groups of hormones is the glucocorticoids. These include cortisol, which is often referred to as the ‘natural stress hormone.’ Cortisol plays a variety of important functions within the body, particularly for metabolism and the immune system. These are produced in the adrenal cortex.

Another group of hormones produced by the adrenals is the mineralocorticoids. These include aldosterone, which plays a key role in maintaining a balance of electrolytes such as sodium and potassium. The mineralocorticoids are produced in the outmost layer of the adrenals, known as the zona glomerulosa.

When insufficient levels of these hormones are produced by your dog’s body, it can have serious health consequences.

What Causes Addison’s Disease in Dogs?

Addison’s disease in dogs occurs when some of the adrenal hormones are produced in insufficient quantities.

Primary hypoadrenocorticism is the classic type of Addison’s, and it means that production of both glucocorticoids and mineralocorticoids is affected. The most likely cause is the body’s own immune system attacking the glands, referred to as an autoimmune process. Less commonly, this can be caused by cancer within the glands, infection, or lack of blood supply. Sometimes for dogs that are being treated for Cushing’s disease, these hormones can have an Addisonian crisis – meaning that the hormone levels are suppressed too far by drugs such as mitotane or trilostane, mimicking Addison’s disease.

Atypical hypoadrenocorticism occurs when there is insufficient production of glucocorticoids but a sufficient amount of mineralocorticoids produced. Sometimes dogs that present as atypical can develop typical Addison's disease in the future.

Secondary hypoadrencorticism can occur when there is a deficiency of one of the hormones within the brain – ACTH (adrenocorticotropic) or CRH (corticotropin). ACTH function is to stimulate the adrenal glands to release cortisol, while CRH is the central regulator to the body’s stress response.

What Are the Early Symptoms of Addison’s Disease in Dogs?

Clinical signs of Addison’s disease usually develop over time and can be nonspecific, mild or vague, and wax and wane over time. Symptoms can also quickly develop into a life-threatening condition. While dogs may experience certain symptoms in the early stages of the disease, they can progress to other symptoms. Some of the most common signs dogs with Addison’s disease will display are:

• Weight loss 
• Lack of appetite 
• Increased water intake and urination 
• Shaking 
• Diarrhea 
• Vomiting 
• Lethargy 
• Weakness 
• Collapse  

Early-stage symptoms include depression and lethargy but can be typically vague and nonspecific. You may notice this if your dog isn’t displaying the energy or willingness to get up from laying down. They seem less playful than usual and less interested in spending time interacting with their favorite toys or other pets and people. 

During the later stages of Addison’s, more serious cases can develop. Your dog may experience a low heart rate, which is known as an Addisonian crisis. This happens as a result of three things: abnormal number of electrolytes in their body, a weak pulse due to dehydration, and an extremely low blood pressure. This will display as sudden weakness, severe vomiting and diarrhea and sometimes, collapse. An Addisonian crisis is considered a medical emergency, and your dog will require immediate veterinary treatment.

Diagnosing Addison’s in Dogs

It can be tricky to diagnose Addison’s and often involves diagnostic tests to help rule out other more common diseases, due to the fact the signs displayed are relatively nonspecific and can occur in a wide range of conditions. In order to diagnose Addison’s disease in dogs, your vet will first take a history by asking questions about when the symptoms started and any other changes you have noticed.

They are likely to take blood tests which typically show elevated levels of potassium and low sodium in the blood for this disease. This is suggestive of Addison’s but not fully diagnostic as these results can be seen in other underlying health problems, such as kidney disease. Sometimes white blood cell count can provide useful additional information at this stage.

An ACTH stimulation test is often performed. This is when the levels of cortisol in your dog’s blood will be measured before and after an injection of ACTH. Dogs with a normal hormone response will show an elevated cortisol level after the ACTH injection, whereas those with Addison’s have reduced ability to produce cortisol hormones and will often show a less marked elevation in levels. 

Chest x-rays, abdominal ultrasound and heart ECG monitoring may also be performed as part of the process.

How to Treat Addison’s Disease in Dogs

While there is no cure for Addison’s in dogs, it can be managed long term with hormone replacement treatment, with many dogs living a long and happy life after diagnosis. 

It may take your veterinarian some time to determine the correct dosage to give your dog, as this is a delicate balance and varies between individuals. You will need to make regular trips to the vet so they can reassess hormone and electrolyte levels. Some types of medication can be taken as tablets, while others may involve a regular injection.

It’s likely that your dog will need to have regular bloodwork to ensure the medication is still at the correct dosage. These tests will usually be more frequent initially, or if your dog changes doses, but your vet will let you know how often your pet needs blood tests.

For more expert tips on your dog’s health, explore our other dog health symptoms and issues articles.