Hypoadrenocorticism (Addison's Disease) in Cats: A Comprehensive Guide

Introduction

Hypoadrenocorticism, often known as Addison's disease, is a disorder characterized by an underactive adrenal cortex. It leads to inadequate production of essential hormones. This article provides a comprehensive overview of the disease in cats.

Definition and synonyms

Hypoadrenocorticism or Addison's disease describes a condition in which there is insufficient production of mineralocorticoids and glucocorticoids by the adrenal cortex .

Synonyms:

• Adrenocortical insufficiency
• Addison's disease (English)

Epidemiology

Although primary hypoadrenocorticism is rare in cats, the age of affected animals is usually between 1 and 14 years. It is particularly evident in young to middle-aged cats. To date, no gender bias has been identified.

Etiology and pathogenesis

Primary hypoadrenocorticism

This form is usually caused by immune-mediated destruction of the adrenal cortex. Other causes may include trauma or bilateral infiltration by lymphoma.

Secondary hypoadrenocorticism

This mainly occurs when steroid hormones (such as megastrol acetate or methylprednisolone) are stopped too quickly. This leads to a reduced release of ACTH and thus a reduced production of glucocorticoids.

Clinical signs of hypoadrenocorticism (Addison's disease) in cats

Feline hypoadrenocorticism (Addison's disease), also known as Addison's disease, is an underactive adrenal gland that can occur in cats. The clinical symptoms of this disease can be varied and sometimes nonspecific, making diagnosis difficult. A thorough knowledge of the clinical signs is crucial to enable timely diagnosis and appropriate treatment.

General weakness and lethargy

• Apathy : Cats with hypoadrenocorticism can be noticeably listless and inactive. They often show less interest in play, food or social interaction.
• Muscle weakness : Muscle strength may be impaired due to an imbalance of electrolytes. This causes affected cats to be less active or have difficulty jumping and climbing.

Nutrition and weight problems

• Anorexia : Loss of appetite or complete lack of appetite is a common symptom. Affected cats may suddenly refuse their food.
• Weight loss : Significant weight loss can occur due to reduced feed intake or metabolic problems.

Digestive problems

• Vomiting : Some cats may vomit repeatedly, which can lead to dehydration.
• Polyuria and polydipsia : Increased thirst (polydipsia) and increased urine output (polyuria) are seen in some cats with this condition.

Cardiovascular symptoms

• Bradycardia : A slowed heartbeat may occur, causing the cat to feel sluggish or even faint.
• Collapse : In severe cases, cats may collapse suddenly, especially during stress or physical exertion.

Other symptoms

• Hypothermia : A lower than normal body temperature may be observed, particularly during clinical examinations.
• Dehydration : Due to vomiting or reduced drinking, cats may appear dehydrated, with dry mucous membranes and sunken eyes.

It is important to emphasize that these symptoms can also occur with other diseases. Therefore, an accurate diagnosis by a veterinarian essential to ensure appropriate treatment. Early detection and treatment of hypoadrenocorticism can be life-saving and significantly improve the quality of life of affected cats.

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Diagnosis

Laboratory tests

Typical findings are:

• Hyponatremia
• Hyperkalemia
• Decreased sodium-potassium ratio
• Azotemia

The ACTH stimulation test in cats

The ACTH stimulation test is a diagnostic test used to assess the function of the adrenal glands in cats. In particular, it is used to distinguish hypoadrenocorticism (Addison's disease) from other diseases.

Basics

ACTH (adrenocorticotropic hormone) is produced by the pituitary gland and stimulates the adrenal cortex to produce and release cortisol, a vital steroid hormone. In cats with hypoadrenocorticism, the adrenal glands do not respond or respond inadequately to ACTH stimulation.

Carrying out the test

1. Basal cortisol measurement : First, a blood sample is taken to determine the basal (baseline) cortisol level. This provides an overview of the cat's current cortisol production.
2. Administration of ACTH : After the initial blood draw, the animal is administered a synthetic form of ACTH, often known as cosyntropin. Administration can be intravenous or intramuscular.
3. Subsequent blood collections : Additional blood samples will be collected 30 and 60 minutes after ACTH administration. These are used to assess the adrenal cortisol response to ACTH stimulation.

Interpretation of the results

• Normal response : In healthy cats, a significant increase in blood cortisol levels is observed following administration of ACTH.
• Inadequate response : No significant increase in cortisol levels is seen in cats with hypoadrenocorticism because their adrenal glands do not respond or respond inadequately to ACTH.

Advantages and limitations

The ACTH stimulation test is considered the gold standard for diagnosing hypoadrenocorticism. However, it is not specific to this disease alone. Other illnesses or medications can affect the test result.

It is important to interpret the test in the context of the animal's clinical signs and other diagnostic results. If the results are unclear or if other diseases that could affect adrenal function are suspected, further tests or examinations may be necessary.

Differential diagnoses of hypoadrenocorticism (Addison's disease) in cats

If hypoadrenocorticism is suspected in a cat, it is important to consider other conditions that may cause similar clinical signs. These other diseases are called differential diagnoses. Accurate differentiation is crucial for correct treatment and prognosis.

1. Gastrointestinal diseases

Gastrointestinal disorders can cause symptoms such as vomiting, diarrhea, loss of appetite, and weight loss, which are also seen in cats with hypoadrenocorticism. Examples of such diseases are:

• Inflammatory bowel disease (EDB)
• gastritis
• Intestinal obstruction

2. Diabetes mellitus

Diabetes mellitus leads to elevated blood sugar levels and can cause symptoms such as increased thirst, increased urine output, weight loss and loss of appetite.

3. Urinary tract infections

A lower urinary tract infection can cause symptoms such as increased thirst, frequent urination, blood in the urine, and pain when urinating.

4. Cardiorespiratory diseases

Heart and lung problems can cause shortness of breath, cough, reduced activity, and other nonspecific symptoms that could be confused with hypoadrenocorticism. Examples are:

• Cardiomyopathy
• Respiratory diseases such as asthma

5. Body cavity effusions

Fluid accumulation in the body cavities (e.g. pleural effusion in the chest or ascites in the abdomen) can lead to non-specific symptoms such as lethargy, loss of appetite and shortness of breath.

Differential diagnoses are crucial to determining the exact cause of a cat's symptoms. A thorough clinical examination, laboratory tests, and imaging tests can help distinguish hypoadrenocorticism from other conditions. It is of utmost importance to determine the exact cause of the symptoms to ensure proper treatment and provide an optimal prognosis for the animal.

Therapeutic approaches to hypoadrenocorticism (Addison's disease) in cats

Therapy for hypoadrenocorticism (Addison's disease) in cats aims to replace the missing adrenal hormones and balance electrolyte imbalances. Here are the detailed therapeutic approaches:

1. Emergency treatment: Acute Addisonian crisis

If a cat enters an acute Addisonian crisis, immediate emergency treatment is required:

• Aggressive infusion therapy : Administration of 0.9% NaCl (saline) solution helps correct dehydration and associated electrolyte imbalances.
• Glucocorticoid administration : After performing the ACTH stimulation test, a glucocorticoid such as prednisolone can be administered intravenously at a dose of 5 to 8 mg/kgBW. This replaces the missing cortisol and helps against shock conditions.

2. Long-term therapy

Mineralocorticoid replacement:

• Fludrocortisone : This medication is administered orally and helps replace the function of mineralocorticoids. The usual dosage is between 0.05 and 0.1 mg/cat BID (twice daily). It helps maintain electrolyte balance and regulate the renin-angiotensin-aldosterone system.

Glucocorticoid replacement:

• Prednisolone : ​​In addition to its use in emergency therapy, prednisolone can also be used for long-term treatment. The dose is between 0.5 and 2 mg/kgBW/day and is administered orally. This replaces the missing cortisol, which is necessary for many body processes.

Alternative treatments:

• Deoxycorticosterone : This is another mineralocorticoid replacement. It is administered subcutaneously at a dosage of 2.0 mg/kg every 20 to 25 days as a depot.

Note on medication dosage:

It is important to carefully follow the manufacturer's dosage recommendations as well as the veterinarian's instructions. Each cat is individual, and the dosage may vary depending on the severity of the disease and the animal's response to therapy. Regular follow-up examinations and blood tests are required to adjust therapy and ensure the cat's health.

The therapeutic approach to hypoadrenocorticism in cats requires careful diagnosis, emergency interventions in acute crises, and long-term hormonal replacement therapy. Regular monitoring by a veterinarian is crucial for the long-term success of the treatment.

Summary Hypoadrenocorticism (Addison's disease) in cats

Hypoadrenocorticism (Addison's disease) in cats is a condition in which the adrenal cortex does not produce enough vital hormones. These hormones are necessary for many body functions, such as electrolyte balance and metabolism.

Hypoadrenocorticism (Addison's disease) in cats can cause a variety of symptoms. These include lethargy, weight loss and general weakness. In the worst case, an Addisonian crisis can occur, which is life-threatening.

To diagnose hypoadrenocorticism (Addison's disease) in cats, an ACTH stimulation test is often performed. This test checks how well the adrenal glands respond to a hormone called ACTH, which normally stimulates hormone production in the adrenal gland.

Treatment of hypoadrenocorticism (Addison's disease) in cats consists primarily of hormone replacement therapy. Cats with this condition require lifelong medication to replace the missing hormones.

There are many possible causes of hypoadrenocorticism (Addison's disease) in cats, from autoimmune diseases to injury to the adrenal glands. Some cats may also develop secondary hypoadrenocorticism if they are taken off certain medications too quickly.

It is important to know that hypoadrenocorticism (Addison's disease) in cats is a very treatable condition. With proper diagnosis and treatment, most cats can live normal, healthy lives.

In summary, hypoadrenocorticism (Addison's disease) in cats is a serious but treatable condition. If you think your cat may be affected, seek veterinary attention immediately. With proper care, your cat can live a long and healthy life despite hypoadrenocorticism (Addison's disease) in cats.

Sources Hypoadrenocorticism (Addison's disease) in cats

• Schmidt, V., Horzinek, MC, Lutz, H., Kohn, B., Forterre, F. (2015). Cat diseases. Enke Publishing