Addison’s Disease (Hypoadrenocorticism)

What is Addison’s disease in dogs?

Addison’s disease in dogs is a hormone deficiency disorder that occurs when the adrenal glands do not produce enough essential hormones. It is also called hypoadrenocorticism and most often affects cortisol and aldosterone, two hormones that help regulate stress response, hydration, blood pressure, and electrolyte balance.

Because these hormones influence many body systems, Addison’s disease can cause vague or shifting signs such as lethargy, vomiting, diarrhea, weakness, poor appetite, dehydration, trembling, or collapse. The condition can become life-threatening during an Addisonian crisis, but many dogs do well once the disease is correctly diagnosed and treated.

What does hypoadrenocorticism mean?

Hypoadrenocorticism means the adrenal cortex is producing too little hormone. “Hypo” means low, “adreno” refers to the adrenal glands, and “corticism” refers to the adrenal cortex, the outer part of the adrenal glands where important hormones are made.

In dogs, hypoadrenocorticism usually means the body does not have enough cortisol, and in typical Addison’s disease, not enough aldosterone. This disrupts the dog’s ability to respond to stress, maintain hydration, and keep sodium and potassium levels in balance.

Why is Addison’s disease called “the great imitator”?

Addison’s disease is called “the great imitator” because its symptoms can look like many other health problems. Dogs with Addison’s may show vomiting, diarrhea, weakness, dehydration, appetite loss, abdominal discomfort, or collapse, which can resemble gastrointestinal disease, kidney problems, pancreatitis, toxin exposure, shock, or intestinal obstruction.

The signs may also come and go, making the condition harder to recognize early. A dog may seem mildly ill, improve for a while, and then become sick again, which is why specific hormone testing is often needed to identify Addison’s disease.

Which dog breeds are more commonly associated with Addison’s disease?

Addison’s disease can affect any breed, including mixed-breed dogs, but some breeds appear to be overrepresented. Breeds commonly associated with hypoadrenocorticism include Standard Poodles, Portuguese Water Dogs, West Highland White Terriers, Great Danes, Bearded Collies, and Nova Scotia Duck Tolling Retrievers.

A breed association does not mean a dog will develop Addison’s disease. It means the condition may deserve added awareness when a dog from a predisposed breed has unexplained or recurring signs such as digestive upset, lethargy, weakness, dehydration, collapse, or poor stress tolerance.

Are West Highland White Terriers prone to Addison’s disease?

West Highland White Terriers are one of the breeds reported to be more commonly associated with Addison’s disease. This does not mean most Westies will develop hypoadrenocorticism, but it does mean the condition may be more relevant to consider when a Westie has recurring vague signs such as intermittent vomiting, diarrhea, lethargy, weakness, poor appetite, dehydration, collapse, or poor recovery after stress.

Breed association is only one piece of context. Addison’s disease cannot be identified by breed alone, and diagnosis still depends on adrenal hormone testing, such as baseline cortisol screening and an ACTH stimulation test.

What hormones are low in dogs with Addison’s disease?

Dogs with Addison’s disease typically have low cortisol, and many also have low aldosterone. Cortisol helps the body respond to stress and maintain normal energy, immune balance, blood sugar support, and cardiovascular function. Aldosterone helps regulate sodium, potassium, hydration, and blood volume.

In typical Addison’s disease, both cortisol and aldosterone are deficient. In atypical Addison’s disease, cortisol is low but aldosterone may remain normal, so sodium and potassium values may not show the classic pattern.

What does cortisol do in dogs?

Cortisol helps dogs respond to stress and maintain normal internal balance. It supports energy metabolism, blood pressure stability, immune regulation, appetite, gastrointestinal function, and the body’s ability to handle illness, travel, boarding, surgery, or other stressors.

When cortisol is too low, a dog may have poor stress tolerance, low energy, weakness, digestive upset, poor appetite, trembling, or collapse. These signs can worsen during stressful events because the body cannot increase cortisol production when it is needed most.

What does aldosterone do in dogs?

Aldosterone helps dogs maintain proper fluid and electrolyte balance. It acts mainly on the kidneys, helping the body retain sodium and water while regulating potassium excretion.

When aldosterone is too low, sodium can drop and potassium can rise. This can lead to dehydration, low blood volume, weakness, slow heart rate, abnormal heart rhythm, and, in severe cases, shock or collapse.

How are cortisol and aldosterone related?

Cortisol and aldosterone are both hormones produced by the adrenal cortex, but they have different roles. Cortisol mainly supports stress response, metabolism, immune balance, and cardiovascular stability, while aldosterone mainly controls sodium, potassium, hydration, and blood volume.

In Addison’s disease, the adrenal glands may fail to produce enough of one or both hormones. Typical Addison’s affects both cortisol and aldosterone, while atypical Addison’s affects cortisol without obvious aldosterone deficiency at first.

Why do Addison’s disease symptoms come and go?

Addison’s disease symptoms can come and go because hormone levels may be low enough to cause illness during stress but not always low enough to cause constant severe signs. A dog may seem tired, nauseous, or have intermittent diarrhea, then appear to recover before the next episode.

Stressful events such as illness, travel, boarding, injury, surgery, or major routine changes can expose the hormone deficiency more clearly. These situations normally require a stronger cortisol response, and dogs with Addison’s disease may not be able to meet that demand.

What is an Addisonian crisis in dogs?

An Addisonian crisis is a severe, potentially life-threatening episode caused by dangerously low adrenal hormone activity. Dogs in crisis may become extremely weak, dehydrated, cold, flat, unresponsive, or unable to stand, and some may show vomiting, diarrhea, collapse, shock, a slow heart rate, or abnormal heart rhythm.

This crisis occurs when the body can no longer maintain circulation, hydration, electrolyte balance, and stress response. It is one of the most serious presentations of Addison’s disease and requires urgent stabilization.

Why can stress trigger collapse in dogs with Addison’s disease?

Stress can trigger collapse in dogs with Addison’s disease because their adrenal glands cannot produce enough cortisol to support the body during increased demand. Events such as illness, travel, boarding, surgery, or intense physical stress normally require a rise in cortisol.

Without enough cortisol, the body may struggle to maintain blood pressure, energy metabolism, circulation, and digestive stability. If aldosterone is also low, dehydration and electrolyte imbalance can further increase the risk of weakness, shock, or collapse.

How can Addison’s disease look like a gastrointestinal blockage?

Addison’s disease can look like a gastrointestinal blockage because it may cause vomiting, appetite loss, abdominal discomfort, hunching, straining, bloating, or slowed intestinal movement. These signs can make it seem as though a dog swallowed a foreign object or has an obstruction.

Imaging may sometimes show gas buildup or reduced gut motility without a clear foreign body. When gastrointestinal signs occur alongside dehydration, weakness, abnormal heart rate, or unusual electrolyte findings, Addison’s disease may remain an important possibility.

What conditions can Addison’s disease mimic in dogs?

Addison’s disease can mimic gastrointestinal upset, intestinal obstruction, pancreatitis, kidney disease, toxin exposure, shock, stress-related diarrhea, dietary sensitivity, and other systemic illnesses. This happens because cortisol and aldosterone affect digestion, hydration, circulation, electrolytes, and overall energy.

The overlap in signs is one reason Addison’s disease can be difficult to diagnose from symptoms alone. Specific testing, especially cortisol testing and ACTH stimulation testing, is often needed to separate Addison’s disease from other conditions.

What is atypical Addison’s disease in dogs?

Atypical Addison’s disease is a form of hypoadrenocorticism in which a dog has low cortisol but does not initially show the classic sodium and potassium changes. These dogs may still produce enough aldosterone to keep electrolytes within normal ranges.

Signs of atypical Addison’s disease are often vague and may include lethargy, poor appetite, intermittent vomiting or diarrhea, poor recovery from stress, or reduced interest in normal activity. Some dogs with atypical Addison’s later progress to typical Addison’s, where aldosterone production also becomes impaired.

Why is atypical Addison’s disease harder to diagnose?

Atypical Addison’s disease is harder to diagnose because routine bloodwork may not show the classic electrolyte pattern of low sodium and high potassium. Without those clues, the condition can resemble chronic digestive upset, stress sensitivity, poor appetite, or other nonspecific illnesses.

Cortisol testing is often the key diagnostic step. A low baseline cortisol may raise suspicion, while an ACTH stimulation test can confirm whether the adrenal glands are able to produce cortisol appropriately.

What causes primary hypoadrenocorticism in dogs?

Primary hypoadrenocorticism in dogs is most often caused by immune-mediated destruction of the adrenal glands. In this form, the body’s immune system mistakenly damages adrenal tissue, reducing the glands’ ability to produce cortisol and, in many cases, aldosterone.

Less commonly, adrenal hormone deficiency may be linked to infections, tumors, congenital adrenal underdevelopment, or other damage affecting the adrenal glands. Regardless of the trigger, the result is inadequate hormone production and reduced ability to maintain normal internal balance.

Can steroid withdrawal cause Addison’s disease in dogs?

Sudden withdrawal from long-term corticosteroid use can cause an Addison-like hormone deficiency in dogs. When a dog receives corticosteroids for an extended period, the body may reduce its own natural cortisol production.

If steroids are stopped too quickly, the adrenal system may not be ready to produce enough cortisol on its own. This is why corticosteroid changes are typically managed carefully, especially after long-term use.

How is Addison’s disease diagnosed in dogs?

Addison’s disease is diagnosed through a combination of clinical signs, bloodwork, electrolyte evaluation, and specific adrenal hormone testing. A veterinarian may suspect Addison’s disease when a dog has recurring vomiting, diarrhea, weakness, dehydration, collapse, low sodium, high potassium, or vague illness that does not fit a clear pattern.

The ACTH stimulation test is considered the confirmatory test. Other diagnostics such as CBC, chemistry panel, urinalysis, imaging, and ECG may help evaluate the dog’s overall condition and rule out similar diseases.

What is a baseline cortisol test used for in dogs?

A baseline cortisol test measures a dog’s resting cortisol level. It is often used as a screening tool when Addison’s disease is suspected, especially in dogs with vague, recurring, or unexplained signs.

A normal baseline cortisol level can make Addison’s disease less likely, while a low result supports further testing. Because a baseline cortisol test does not fully confirm Addison’s disease by itself, an ACTH stimulation test is usually needed when suspicion remains.

What does an ACTH stimulation test show?

An ACTH stimulation test shows whether the adrenal glands can produce cortisol when stimulated. ACTH is a hormone signal that normally tells the adrenal glands to release cortisol.

In a healthy dog, cortisol levels rise after ACTH is given. In a dog with Addison’s disease, cortisol remains low before and after stimulation, showing that the adrenal glands cannot respond appropriately.

Why are sodium and potassium important in Addison’s disease?

Sodium and potassium are important in Addison’s disease because they reflect aldosterone’s role in fluid and electrolyte balance. Aldosterone helps the body retain sodium and water while regulating potassium levels through the kidneys.

When aldosterone is low, sodium may fall and potassium may rise. This imbalance can contribute to dehydration, weakness, slow heart rate, abnormal heart rhythm, low blood volume, shock, and collapse.

How is Addison’s disease treated in dogs?

Addison’s disease is treated with lifelong hormone replacement. Dogs with cortisol deficiency typically receive a glucocorticoid such as prednisone, while dogs with typical Addison’s also need aldosterone replacement through medications such as DOCP injections or fludrocortisone.

Treatment is adjusted based on the dog’s clinical response, electrolyte levels, and overall health. Once hormone levels are stabilized, many dogs regain normal appetite, hydration, strength, and energy.

Do dogs with Addison’s disease need lifelong treatment?

Dogs with Addison’s disease usually need lifelong treatment because the adrenal glands are no longer producing enough essential hormones. Medication replaces the missing cortisol and, in typical Addison’s disease, the missing aldosterone activity needed for electrolyte and hydration balance.

Routine monitoring helps ensure the dose remains appropriate over time. Adjustments may be needed during illness, growth, major stress, seasonal changes, or shifts in the dog’s overall health.

Can dogs with Addison’s disease live normal lives with treatment?

Dogs with Addison’s disease can often live normal, active lives once the condition is diagnosed and properly managed. Hormone replacement helps restore the body’s ability to maintain hydration, electrolyte balance, appetite, energy, and stress response.

Long-term success depends on consistent medication, monitoring, and recognition of situations that may increase stress on the body. With stable treatment, many dogs return to normal routines and maintain a good quality of life.

What is the difference between hypoadrenocorticism and hypothyroidism in dogs?

Hypoadrenocorticism and hypothyroidism are both endocrine disorders, but they affect different glands and different hormones. Hypoadrenocorticism, or Addison’s disease, involves low adrenal hormones such as cortisol and sometimes aldosterone, while hypothyroidism involves low thyroid hormone.

The symptoms can overlap because both conditions may cause low energy, weakness, poor appetite, or changes in activity. The key difference is that Addison’s disease affects stress response, hydration, sodium, potassium, and circulation, while hypothyroidism mainly slows metabolism and is more often associated with weight gain, cold intolerance, skin changes, hair thinning, and a dull coat.

Why do hypoadrenocorticism and hypothyroidism sound similar?

Hypoadrenocorticism and hypothyroidism sound similar because both names use “hypo,” which means low or too little. In hypoadrenocorticism, the low hormone output comes from the adrenal cortex. In hypothyroidism, the low hormone output comes from the thyroid gland.

The rest of the word identifies the gland or body system involved. “Adreno” refers to the adrenal glands, while “thyroid” refers to the thyroid gland in the neck. This distinction matters because the two conditions affect different hormones, require different tests, and are managed with different types of hormone replacement.

What is the difference between Addison’s disease and Cushing’s disease in dogs?

Addison’s disease and Cushing’s disease are opposite types of adrenal hormone imbalance. Addison’s disease, or hypoadrenocorticism, occurs when adrenal hormone levels are too low. Cushing’s disease, or hyperadrenocorticism, occurs when cortisol levels are too high.

The signs can look different. Addison’s disease is often associated with weakness, vomiting, diarrhea, dehydration, low sodium, high potassium, collapse, or poor stress tolerance. Cushing’s disease is more often associated with increased thirst and urination, increased appetite, panting, a pot-bellied appearance, thin skin, hair loss, and muscle weakness.

What is the difference between hypoadrenocorticism and hyperadrenocorticism?

Hypoadrenocorticism means the adrenal cortex is underactive, while hyperadrenocorticism means the adrenal cortex is overactive or being overstimulated. “Hypo” means too little, and “hyper” means too much.

In dogs, hypoadrenocorticism is another name for Addison’s disease and usually involves low cortisol with or without low aldosterone. Hyperadrenocorticism is another name for Cushing’s disease and usually involves excess cortisol. Because the hormone directions are opposite, the testing, monitoring, and treatment goals are different.