Cushing's Disease

Because cortisol affects metabolism, immunity, and fluid balance simultaneously, Cushing's produces an unusually broad cluster of signs:

• Pot-bellied appearance from abdominal muscle wasting and fat redistribution
• Dramatic increase in thirst and urination — often the first sign owners notice
• Increased appetite and begging for food
• Excessive panting, even at rest or in cool environments
• Symmetrical hair loss on the trunk (body) while the head and legs often stay normal
• Thin, fragile, bruise-prone skin; sometimes visible blood vessels through the skin
• Lethargy and reluctance to exercise
• Recurrent urinary tract infections or skin infections that are slow to clear
• Calcinosis cutis — hard, white calcium deposits under the skin (in some dogs)

Because so many of these signs mimic ordinary aging, Cushing's disease is often diagnosed well after it begins. If several of these signs are present together in a middle-aged to older dog, bloodwork is warranted.

Understanding the cause of Cushing's disease matters because the treatment differs between pituitary-dependent and adrenal-dependent forms:

• Pituitary-dependent (PDH) — accounts for roughly 80–85% of cases; a pituitary microadenoma (usually benign) secretes too much ACTH, which over-stimulates both adrenal glands
• Adrenal-dependent — a tumor (adenoma or carcinoma) on one adrenal gland secretes cortisol directly; accounts for 15–20% of cases
• Iatrogenic Cushing's — caused by prolonged or high-dose corticosteroid therapy (prednisone, etc.); resolves gradually when steroids are tapered

Risk factors include:

• Age — most dogs are seven years or older at diagnosis
• Breed — Poodles, Dachshunds, Boston Terriers, Boxers, and Beagles are over-represented
• Sex — adrenal tumors are more common in female dogs

No single test is 100% sensitive and specific for Cushing's disease, so we use a combination of screening and confirmatory testing alongside abdominal imaging:

• Urine cortisol-to-creatinine ratio (UCCR) — a useful screening test done on an early-morning urine sample collected at home; a normal result largely rules out Cushing's
• Low-dose dexamethasone suppression test (LDDST) — the most sensitive confirmatory test; dogs with Cushing's fail to suppress cortisol normally after a small dexamethasone dose
• ACTH stimulation test — preferred when iatrogenic Cushing's is suspected, and used to monitor treatment response with mitotane
• High-dose dexamethasone suppression test or endogenous ACTH — helps distinguish PDH from adrenal-dependent disease
• Abdominal ultrasound — essential to evaluate adrenal gland size and detect masses; our in-house ultrasound lets us examine the adrenals the same day
• CT scan — used for surgical planning if an adrenal tumor is identified; our on-site CT provides detailed imaging without referral

Treatment depends on whether Cushing's is pituitary-dependent, adrenal-dependent, or iatrogenic:

• Trilostane (Vetoryl) — the most commonly used medical treatment for PDH; given once or twice daily, it blocks cortisol synthesis in the adrenal gland; dose is individualized with regular monitoring
• Mitotane (Lysodren) — an older alternative that selectively destroys part of the adrenal cortex; highly effective but requires careful induction and ongoing monitoring
• Adrenalectomy — surgical removal of an adrenal tumor, performed by Dr. Alan Schulman; can be curative for adrenal-dependent Cushing's when the tumor is resectable; requires intensive perioperative care
• Tapering corticosteroids — for iatrogenic Cushing's; no additional drug therapy is needed, but the taper must be gradual to avoid precipitating Addison's disease

Dogs on medical treatment require regular recheck bloodwork (ACTH stimulation testing) to ensure the dose is controlling cortisol without oversuppressing the adrenals — both extremes are harmful.

If your dog has developed a pot belly, can't stop drinking, or seems exhausted despite eating well, a Cushing's work-up is a smart next step — especially if the dog is older and several signs are present together. While the disease is rarely a same-day emergency, untreated Cushing's causes progressive organ damage and makes other conditions (infections, diabetes, high blood pressure) much harder to control. Our team in Calabasas runs the full diagnostic panel and abdominal ultrasound in-house, so you can often have answers in a single appointment. Book an appointment today.