Serious severity

Cushing's Disease (Hyperadrenocorticism)

A rare hormonal disorder in which the adrenal glands produce too much cortisol. Uncommon in cats but serious — it is most often seen alongside hard-to-control diabetes.

⚠️ Common symptoms

Increased thirst and urinationIncreased appetitePot-bellied appearanceThin, fragile, easily-torn skinHair thinning or lossPoor coat and slow wound healingDiabetes that resists insulin

Cushing's disease, known medically as hyperadrenocorticism, is a condition of hormonal excess: the body is flooded with too much cortisol, the hormone that normally helps it respond to stress, regulate metabolism and control inflammation. In small, well-timed amounts cortisol is essential. In chronic excess it becomes corrosive — thinning the skin, wasting muscle, weakening the immune system and driving up blood sugar.

In cats the disease is decidedly uncommon, which is part of what makes it dangerous: because vets and owners rarely expect it, it can go unrecognised for a long time. The classic picture is an older cat that is drinking and urinating far more than usual, often ravenously hungry, developing a sagging pot-bellied profile as fat redistributes and abdominal muscles weaken. The most striking and almost unique feature of feline Cushing's is its effect on the skin, which can become so thin and fragile that it tears or bruises with ordinary handling — a sign that should always prompt urgent veterinary attention.

The great majority of feline cases are tangled up with diabetes mellitus. Excess cortisol works directly against insulin, so a cat with undiagnosed Cushing's often presents first as a diabetic whose blood sugar simply will not come under control no matter how much insulin is given. In these cats, identifying and treating the Cushing's is frequently the key that finally unlocks good diabetic control.

Reaching a diagnosis takes patience. There is no single perfect test; vets combine the clinical picture with blood and urine analysis, specialised hormone-stimulation or suppression tests, and ultrasound or advanced imaging to look for an adrenal or pituitary tumour. Treatment is then tailored to the cause — surgery for an isolated adrenal tumour, medication or radiation for pituitary disease — and always alongside careful management of any accompanying diabetes. Feline Cushing's is a serious diagnosis, but with accurate identification and committed monitoring many cats can be stabilised and made comfortable.

🔍 Causes

Cushing's disease results from chronic over-production of cortisol, the body's main stress hormone. In cats the most common cause is a small tumour of the pituitary gland at the base of the brain, which over-stimulates the adrenal glands; less often a tumour of an adrenal gland itself is to blame. A third form, iatrogenic Cushing's, is caused by long-term use of corticosteroid medication — though cats are far more resistant to this than dogs. The condition is genuinely rare in cats and usually appears in middle-aged to older animals.

🛡 Prevention

There is no way to prevent the tumours that cause naturally-occurring Cushing's disease. The one avoidable form is steroid-induced (iatrogenic) Cushing's, so long courses of corticosteroids should only be used under veterinary guidance and tapered rather than stopped abruptly. Because feline Cushing's so often travels with diabetes, any diabetic cat whose blood sugar cannot be controlled despite rising insulin doses should be investigated for an underlying hormonal driver.

💊 Treatment

Treatment depends on the cause. Where a single adrenal tumour is responsible, surgical removal can be curative. Pituitary-driven disease is harder to manage and may be treated with medication (such as trilostane) to suppress cortisol production, or in some centres with radiation therapy. Because most feline cases occur alongside diabetes, controlling the Cushing's often makes a previously unmanageable diabetes far easier to regulate. Treatment requires close veterinary monitoring with regular blood tests.

When to see a vet: See your vet if an older cat develops marked thirst and urination, a pot-bellied shape, or skin that becomes thin and tears or bruises easily — the fragile, paper-like skin of advanced feline Cushing's is a red-flag sign. Any diabetic cat that needs ever-larger insulin doses without improving warrants prompt testing. Diagnosis usually involves blood and urine tests plus specialised hormone-stimulation tests and imaging of the adrenal glands.

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⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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