Canine Cushing's disease (hyperadrenocorticism)

Symptoms an owner can spot at home

• Dramatically increased thirst (polydipsia) and urination (polyuria)—often the first thing owners notice
• Increased appetite, sometimes ravenous
• Pot-bellied appearance from abdominal muscle weakness and liver enlargement
• Thinning coat, symmetric truncal hair loss, thin skin that bruises easily, recurrent skin infections
• Reduced exercise tolerance, panting at rest, muscle weakness

When to see a vet

• New or worsening thirst and urination in a middle-aged or senior dog—never normal, always investigate
• Recurrent skin or urinary infections without an obvious cause
• Sudden behavioural change, neurological signs, or collapse—large pituitary tumours can cause neurological compression
• If iatrogenic—a dog on long-term steroid therapy developing Cushing's signs—never stop steroids abruptly; taper under vet direction

What it is

Cushing's disease is chronic excess cortisol exposure. The most common form (~80–85% of cases) is pituitary-dependent—a small benign pituitary tumour drives ACTH overproduction, which in turn drives the adrenal glands. Adrenal-dependent disease (~15–20%) is a tumour on the adrenal gland itself. A third form, iatrogenic Cushing's, is the predictable consequence of long-term high-dose steroid therapy.

It is primarily a middle-aged-to-senior small-breed disease, though any breed can be affected. Dachshunds, Poodles, Beagles, and several terrier breeds are over-represented. The disease progresses over months; owners often dismiss early signs as normal aging until thirst and urination become impossible to ignore.

How vets diagnose it

Diagnosis is two-step. First, screening tests: routine bloodwork and urinalysis flag classic markers (raised alkaline phosphatase, dilute urine). Then confirmatory endocrine tests—most commonly a low-dose dexamethasone suppression test (LDDS) or ACTH stimulation test. Differentiating pituitary from adrenal disease requires abdominal ultrasound and sometimes high-dose dexamethasone testing or endogenous ACTH measurement.

Treatment overview

Editorial overview only—your vet builds the plan. Pituitary-dependent disease is treated medically with adrenal-suppressing drugs (trilostane is the modern standard), with regular monitoring blood tests to titrate dose. Adrenal-dependent disease may be managed medically or surgically depending on the tumour. Iatrogenic Cushing's is resolved by a careful steroid taper. Dietary management focuses on consistent calorie control and supporting comorbidities (urinary, dermatologic, orthopaedic).

What buyers can do

• Make fresh water continuously available; restricting water for a polyuric dog is unsafe.
• Expect more accidents—keep an enzymatic urine cleaner on hand and add toilet breaks rather than punishing the dog.
• Keep the dog at lean body weight; the increased appetite of Cushing's pushes most dogs toward weight gain unless feeding is measured.
• Provide a soft, washable bed—Cushing's dogs often develop thin, easily-bruised skin and pressure sores.
• Never skip monitoring bloodwork. Trilostane dose changes happen by lab result, not by how the dog seems on the day.