The Dog Who Drinks Everything, Eats Everything, and Seems to Be Changing Shape
If your dog has developed a ravenous appetite, drinks water incessantly, has a pot-bellied appearance despite not being overweight, and seems to have aged overnight — these signs together should prompt a conversation with your vet about Cushing's disease. Hyperadrenocorticism, to use its clinical name, is one of the most common endocrine disorders in dogs, particularly in middle-aged to older animals. It is manageable, but it requires a correct diagnosis and long-term commitment.
What Cushing's Disease Actually Is
Cushing's disease occurs when the body produces chronically excessive amounts of cortisol, the primary stress hormone secreted by the adrenal glands. Cortisol is essential for life — it regulates metabolism, immune function, and the body's stress response. The problem arises when the regulatory system breaks down and cortisol production becomes uncontrolled.
There are three forms of the disease:
- Pituitary-dependent hyperadrenocorticism accounts for roughly 80 to 85 per cent of cases. A benign tumour on the pituitary gland produces excess ACTH, which in turn stimulates both adrenal glands to overproduce cortisol.
- Adrenal-dependent hyperadrenocorticism involves a tumour on one adrenal gland itself — either benign or malignant — directly secreting excess cortisol.
- Iatrogenic Cushing's syndrome is caused by prolonged administration of corticosteroid medications such as prednisolone. This form resolves when the medication is carefully tapered under veterinary guidance.
The Signs That Should Prompt Investigation
Cushing's disease develops gradually, and many owners attribute the early signs to normal ageing. Knowing what to look for can lead to earlier diagnosis and a better quality of life for your dog.
- Polydipsia and polyuria — drinking and urinating far more than usual
- Polyphagia — constant hunger, often accompanied by food-seeking behaviour and weight gain
- Pot-bellied abdomen caused by muscle wasting and redistribution of fat
- Bilateral symmetrical hair loss, usually sparing the head and limbs
- Thin, fragile skin that bruises easily or develops calcium deposits
- Muscle weakness and exercise intolerance
- Panting at rest or at night
- Recurrent urinary tract infections or skin infections
The combination of increased thirst, increased appetite, and a changed body shape is particularly characteristic. Any dog displaying this triad warrants prompt veterinary assessment.
Diagnosing Cushing's Disease
Diagnosis is notoriously nuanced. No single test is perfectly definitive, and a combination of clinical signs, routine blood work, urinalysis, and specific endocrine tests is typically required.
The most commonly used tests are the low-dose dexamethasone suppression test and the ACTH stimulation test. Each has different strengths — your vet will recommend one or both based on the clinical picture. Ultrasound of the abdomen is useful for identifying adrenal tumours and assessing gland size, which helps differentiate pituitary-dependent from adrenal-dependent disease.
Because many signs of Cushing's overlap with hypothyroidism, diabetes mellitus, and other conditions, a thorough diagnostic workup is essential before treatment begins. Starting treatment for Cushing's in a dog that does not have it can cause serious harm.
Treatment Options
Medical Management
For pituitary-dependent Cushing's, medical management is the most common approach. Trilostane is the preferred medication in the UK and Europe — it works by blocking cortisol synthesis in the adrenal glands. It requires careful dose titration and regular monitoring via ACTH stimulation tests, particularly in the first year of treatment. Mitotane is an alternative used in some countries, with a different mechanism and monitoring protocol.
Medical treatment controls the disease rather than curing it. Dogs typically require lifelong treatment, regular monitoring, and occasional dose adjustments. When managed well, most dogs experience a significant improvement in quality of life.
Surgical and Radiation Options
Adrenal tumours may be treated surgically if the mass is localised and the dog is a suitable anaesthetic candidate. Pituitary tumours causing neurological signs may be treated with radiation therapy in specialist centres. These options are not universally available and carry their own risks, but they can offer the possibility of remission in selected cases.
Living With a Dog With Cushing's Disease
Management of Cushing's disease is a partnership between owner and vet. Owners play a vital role in recognising when their dog is not responding to treatment or when signs of over-suppression — lethargy, reduced appetite, vomiting, weakness — appear. Over-suppression of cortisol can precipitate an Addisonian crisis, which is a medical emergency.
- Keep all scheduled monitoring appointments — do not skip ACTH stimulation tests
- Contact your vet immediately if your dog seems collapsed, weak, or unresponsive, particularly after a medication change
- Keep a simple diary of water intake and appetite as a baseline — changes are easier to detect when you have something to compare against
- Manage secondary conditions such as urinary tract infections promptly, as immunosuppression from excess cortisol makes dogs more susceptible
- Discuss dietary adjustments with your vet — some dogs benefit from a lower-calorie or higher-protein diet during treatment
Cushing's disease is not curable in most cases, but it is controllable. With correct diagnosis, appropriate treatment, and consistent monitoring, many dogs with Cushing's disease enjoy comfortable, active lives for years after their diagnosis.