Cushing’s Disease in Dogs: A Comprehensive Overview

Cushing’s disease, also known as hyperadrenocorticism, is a common endocrine disorder in dogs, particularly older ones. It occurs when the adrenal glands produce excessive cortisol, a vital hormone involved in stress response, metabolism, and immune function. While essential in normal amounts, prolonged overexposure to cortisol can lead to a variety of health problems.

Diagnosis

Diagnosing Cushing’s can be challenging, as its symptoms often mimic those of other age-related conditions. Common signs include:

• Increased thirst and urination (polyuria and polydipsia)
• Increased appetite (polyphagia)
• Pot-bellied appearance
• Hair loss, particularly on the trunk
• Thinning skin
• Muscle weakness
• Lethargy
• Panting

If Cushing’s is suspected, your veterinarian will perform a thorough physical examination and run various diagnostic tests. These typically include:

• Complete Blood Count (CBC) and Chemistry Panel: These tests assess overall organ function and can reveal changes suggestive of Cushing’s, such as elevated liver enzymes and glucose levels.
• Urine Analysis: Evaluates urine concentration and screens for urinary tract infections, which are more common in dogs with Cushing’s.
• Low-Dose Dexamethasone Suppression Test (LDDST): This is a commonly used test to measure cortisol levels after administering a small dose of dexamethasone. It helps determine if the adrenal glands are overproducing cortisol and if the overproduction is suppressible.
• ACTH Stimulation Test: This test measures cortisol levels before and after injecting synthetic ACTH (adrenocorticotropic hormone), which stimulates the adrenal glands. An exaggerated response indicates Cushing’s disease.
• Abdominal Ultrasound: Can help visualize the adrenal glands to identify tumors or enlargement. In some cases, an abdominal CT scan or MRI may be recommended.

These tests can help differentiate between pituitary-dependent Cushing’s (PDH), which is the most common form, and adrenal-dependent Cushing’s (ADH), where a tumor on the adrenal gland is the cause.

Treatment

Treatment for Cushing’s disease aims to reduce cortisol levels and alleviate clinical signs. The primary treatment options are:

• Medication:
  • Trilostane: The most commonly prescribed medication, trilostane inhibits cortisol production. It requires careful monitoring with regular ACTH stimulation tests to adjust the dosage.
  • Mitotane (Lysodren): A less commonly used medication that destroys cortisol-producing cells in the adrenal glands. It requires close monitoring and can have more significant side effects.
• Surgery: For ADH caused by an adrenal tumor, surgical removal of the affected adrenal gland may be an option. This is a more invasive procedure but can be curative.

Side Effects

Both medications and surgery can have potential side effects. With medication, these can include:

• Lethargy
• Loss of appetite
• Vomiting
• Diarrhea
• Adrenal crisis (Addisonian crisis), a life-threatening condition caused by excessively low cortisol levels.

Close monitoring by your veterinarian is crucial to manage potential side effects and ensure the correct dosage of medication. Surgical risks include bleeding, infection, and the possibility of Addisonian crisis.

Cushing’s disease is a manageable condition with appropriate diagnosis and treatment. Regular veterinary checkups and close observation of your dog’s behavior are essential for maintaining their quality of life.