Addison’s Disease: The Great Pretender

Why it’s called “The Great Pretender,” and how we manage it differently.

Addison’s disease is one of those conditions that can quietly fly under the radar for months or even years. It doesn’t always announce itself clearly. Instead, it mimics many other illnesses, mild tummy upsets, vague lethargy, and intermittent weakness, which is exactly why it’s often referred to as “The Great Pretender.”

At Casey and Cranbourne Veterinary Hospital, we regularly diagnose and manage Addison’s disease, including complex and emergency cases. Over the past several years, our team, led by Dr Leanne Versteege, has developed extensive experience using advanced, low-dose treatment protocols that allow many dogs to live long, stable, and very normal lives.

Addison’s disease (hypoadrenocorticism) occurs when a dog’s adrenal glands don’t produce enough essential hormones.

These hormones play a vital role in everyday body function – especially during stress.

What the adrenal glands normally do

When these hormones are lacking, the body struggles to regulate fluids, electrolytes, and stress, leading to the often vague but serious symptoms of Addison’s disease.

Addison’s disease can affect any dog, at any age, male or female. However, it’s more commonly diagnosed in young to middle-aged dogs and is more frequently seen in certain breeds.

Breeds with an increased risk of Addison’s disease include:

• Standard Poodles
• Bearded Collies
• Old English Sheepdogs
• Nova Scotia Duck Tolling Retrievers
• Weimaraners
• Leonbergers

That said, mixed-breed dogs can absolutely develop Addison’s too – we see it across a wide range of patients from Cranbourne, Clyde, Lynbrook, Seaford and surrounding suburbs.

The early signs of Addison’s disease are often subtle and inconsistent. Dogs may seem “a bit off” rather than obviously unwell.

Common early symptoms of Addison’s disease:

• Lethargy or low energy
• Reduced appetite
• Vomiting or diarrhoea
• Weight loss
• Muscle weakness or shaking
• Pain or discomfort in the hind legs
• Reluctance to jump, exercise, or climb stairs

These signs may come and go over time, which is why Addison’s is frequently misdiagnosed or only identified once a dog becomes critically unwell.

If the disease progresses untreated, dogs can experience an Addisonian crisis, which is life-threatening.

This happens when electrolyte imbalances, particularly dangerously high potassium, interfere with heart function and blood pressure.

Signs of an Addisonian crisis

Emergency signs

• Collapse or extreme weakness
• Severe vomiting or diarrhoea
• Tremors or shaking
• Abnormal heart rhythms
• Profound dehydration

If your dog shows these signs, immediate veterinary care is essential.

We offer same-day emergency assessment and treatment for Addisonian crises and do not delay care when minutes matter.

There is only one definitive test for Addison’s disease: the ACTH stimulation test.

At our clinic, diagnosis is often supported by:

• In-house blood testing with same-day results
• Electrolyte assessment (sodium and potassium levels)
• Pattern recognition from years of clinical experience

This allows us to identify Addison’s earlier, sometimes before a crisis occurs.

Once diagnosed, Addison’s disease is manageable. Most dogs go on to live happy, active lives with the right treatment and monitoring.

Standard treatment components

Dr Leanne Versteege has been managing Addison’s disease using low-dose Percorten-V (Zycortal) protocols since 2016, following international research and years of real-world clinical data.

This approach is not commonly used in general practice, but we’ve successfully managed multiple long-term patients, including Violet, Patches, and April, using carefully tailored dosing and close monitoring.

Why low-dose protocols matter

This depth of experience allows us to manage many Addison’s cases in-house, without immediate referral, while still recognising when specialist input is needed.

Once stabilised, dogs with Addison’s can:

• Enjoy normal exercise and routines
• Undergo surgery safely with planning
• Live full, happy lives

Ongoing care is key, and we work closely with owners to ensure monitoring feels manageable and supportive, never overwhelming.

If your dog is showing unexplained vomiting, lethargy, weakness, or collapse, especially if symptoms seem to come and go, trust your instincts and call us.

We offer:

• Same-day appointments where possible
• In-house diagnostics with rapid results
• Calm, thorough, non-judgemental care

Contact Casey and Cranbourne Veterinary Hospital to book an appointment or discuss your concerns.