Cushing’s Disease (Hyperadrenocorticism)

Cushing’s Disease (Hyperadrenocorticism)

Species: Dog

Breeds Affected: All Breeds (usually middle-aged and older; poodles, terriers, dachshunds among breeds often affected)

Cushing’s disease is an endocrine disorder where the adrenal glands secrete excess cortisol. In 80–85% of cases it's due to a benign pituitary gland tumor (pituitary-dependent Cushing’s); the remaining cases result from an adrenal tumor. Elevated cortisol over time causes a variety of metabolic disturbances. It typically affects dogs >6 years old. If untreated, Cushing’s can lead to complications like diabetes, high blood pressure, or infections.

• Symptoms tend to develop gradually. Common signs are increased thirst and urination (dogs may begin having accidents or need more frequent outings)
• increased appetite (often very food-motivated)
• and excessive panting. Owners often notice a “pot-bellied” abdomen due to enlarged liver and weakened abdominal muscles. The skin thins and hair loss occurs – often a symmetric alopecia along the flanks. Recurrent skin infections or delayed wound healing can happen due to cortisol’s immune suppression. Muscle weakness
• lethargy
• and infertility in intact dogs are other possible signs.

Cushing’s is usually managed with medication to reduce cortisol production. The most common treatment is medical management with drugs like trilostane (which blocks adrenal cortisol synthesis) or sometimes mitotane (which selectively destroys part of the adrenal cortex). These drugs are given daily and adjusted based on monitoring tests. In the uncommon case of an adrenal tumor that is operable, surgery (adrenalectomy) can be curative, but surgery is risky and not widely available. Dogs on medical therapy require periodic bloodwork (ACTH stimulation tests) to ensure proper control. With treatment, symptoms improve: drinking and appetite normalize, and skin/hair changes gradually resolve. Lifelong treatment and monitoring are typically required.

Trilostane (Vetoryl) is the only FDA-approved drug for canine Cushing’s and is the first-line medication. It inhibits an enzyme in the adrenal gland, thus lowering cortisol levels. It is given once or twice daily with food. Another medication, mitotane (Lysodren), is an older therapy that destroys cortisol-producing cells and is used in some cases. Both require careful dosing and regular ACTH stimulation tests to avoid causing Addison’s disease (too little cortisol). If a pituitary tumor is large, brain-focused treatments (radiation therapy) might be considered, but most are treated medically. Ketoconazole and selegiline are other less common medical options. Throughout treatment, dogs may also need medications for secondary issues (e.g., insulin for cortisol-induced diabetes or antibiotics for recurring infections) until Cushing’s is controlled.