Canine Cushing’s disease, or hyperadrenocorticism, is a common endocrine disorder, particularly in older dogs. Accurate diagnosis is crucial for effective management and improving the quality of life for affected animals. While treatment focuses on managing cortisol levels, understanding the diagnostic process is the first critical step for pet owners and veterinarians alike.
Initially, the diagnosis of Cushing’s disease in dogs often relies on recognizing clinical signs. These can include increased thirst and urination (polyuria and polydipsia), increased appetite (polyphagia), panting, lethargy, and a characteristic pot-bellied appearance. Skin changes, such as hair loss, thinning skin, and secondary skin infections, are also frequently observed. However, these signs are not exclusive to Cushing’s disease and can overlap with other conditions, necessitating specific diagnostic tests.
Several tests are available to confirm a diagnosis of Cushing’s disease in dogs. The ACTH stimulation test is frequently used to assess adrenal gland function. This test involves measuring cortisol levels before and after the administration of synthetic ACTH. In dogs with Cushing’s disease, the adrenal glands overreact to ACTH stimulation, resulting in an exaggerated increase in cortisol production. Another commonly employed test is the low-dose dexamethasone suppression test (LDDST). This test evaluates the body’s feedback mechanism to suppress cortisol production. In healthy dogs, dexamethasone, a synthetic glucocorticoid, should suppress cortisol release. However, in dogs with Cushing’s disease, this suppression is either absent or reduced.
While these tests are valuable, it’s important to note that no single test is 100% accurate, and results should always be interpreted in conjunction with clinical signs and other diagnostic findings. In some cases, differentiating between pituitary-dependent hyperadrenocorticism (PDH), the most common form, and adrenal-dependent hyperadrenocorticism (ADH) is necessary as it can influence treatment strategies. Advanced imaging, such as abdominal ultrasound, may be used to visualize the adrenal glands and identify adrenal tumors, suggesting ADH.
Once Cushing’s disease is diagnosed, treatment options are considered. Trilostane, an adrenal enzyme inhibitor, is often the first-line medication for managing hyperadrenocorticism in dogs. It works by reducing the production of cortisol by the adrenal glands. The original article excerpt highlights trilostane as a treatment of choice, mentioning a starting dosage of 1–3 mg/kg given with food every 12 hours. Regular monitoring is crucial during trilostane treatment, often using the ACTH stimulation test to ensure cortisol levels are appropriately managed and to avoid hypoadrenocorticism (Addison’s disease), a potential side effect of excessive cortisol suppression.
Mitotane (o,p′-DDD) is another medication used, particularly for PDH and sometimes for atypical or sex steroid hyperadrenocorticism and calcinosis cutis, where it may be more effective than trilostane. Mitotane is an adrenolytic agent, meaning it destroys cortisol-producing cells in the adrenal glands. The excerpt details induction and maintenance dosages for mitotane, along with the importance of monitoring for hypoadrenocorticism and performing ACTH response tests to assess treatment efficacy. It’s also noted that adrenal tumors can be more resistant to mitotane, sometimes requiring higher doses compared to PDH management, and surgical removal might be a more favorable approach for adrenal-dependent Cushing’s.
In conclusion, diagnosing Cushing’s disease in dogs involves recognizing clinical signs and employing specific diagnostic tests like the ACTH stimulation test and LDDST. Understanding the nuances of these tests and potentially utilizing imaging techniques are key to accurate diagnosis and differentiating between PDH and ADH. Treatment, frequently initiated with trilostane or mitotane, requires careful monitoring and dosage adjustments to effectively manage cortisol levels and improve the dog’s wellbeing. Early diagnosis and appropriate management are vital for dogs suffering from Cushing’s disease.
