Cushing's Disease in Dogs: A UK Owner's Guide to Signs, Diagnosis, and Treatment

What Cushing's actually is

Cushing's disease is the result of excess cortisol in the body. Cortisol is the body's main stress hormone — useful in short bursts (responding to threat, fasting, infection) but damaging at chronically elevated levels. In Cushing's, cortisol stays high all the time, which gradually disrupts metabolism, immune function, skin and coat quality, muscle mass, and water balance.

Two causes account for nearly all canine cases:

• Pituitary-dependent Cushing's (about 80–85% of cases): A small benign tumour in the pituitary gland (in the brain) overproduces the hormone that tells the adrenal glands to make cortisol. Both adrenals enlarge.
• Adrenal-dependent Cushing's (15–20%): A tumour in one adrenal gland (often, but not always, malignant) directly overproduces cortisol.

A third form — iatrogenic Cushing's — is caused by long-term high-dose steroid medication. Once the medication is gradually withdrawn, the condition resolves.

Most commonly affected breeds include Poodles, Dachshunds, small terriers (Yorkshire, Jack Russell, Boston, Cairn), Beagles, Boxers, and Staffordshire Bull Terriers, though any breed can develop it. Most dogs are diagnosed between 8 and 12.

Warning signs to watch for

The early signs are easy to mistake for ageing:

• Increased thirst and urination — often the first thing owners notice. A formerly clean dog may start having accidents.
• Increased appetite — a noticeably food-obsessed older dog
• A pot-bellied appearance — muscle loss in the abdomen plus enlargement of the liver give a saggy belly
• Symmetrical hair loss along the body (rarely on the head or legs), with thin or fragile skin
• Slow regrowth of clipped fur
• Recurrent skin infections despite treatment
• Recurrent urinary tract infections
• Lethargy or reduced exercise tolerance
• Excessive panting, even when at rest
• Muscle weakness — reluctance to climb stairs or jump
• Calcified plaques in the skin in advanced cases (a chalky white deposit, often on the back)

The combination of increased thirst + pot belly + thinning coat in an older dog is highly suggestive. If you notice the thirst increase specifically (refilling the bowl noticeably more often), book a vet check.

What diagnosis involves

Diagnosing Cushing's takes more steps than many other conditions because no single test is reliable on its own. A typical UK workup:

1. Clinical examination — the visible signs above are often suggestive on their own.
2. Routine blood and urine tests — looking for typical Cushing's patterns (raised liver enzymes, dilute urine, raised cholesterol). These don't confirm the diagnosis but flag the suspicion.
3. A specific dynamic test — the most common in UK general practice is the ACTH stimulation test (a baseline blood sample, an injection of ACTH, then a second blood sample one hour later). The low-dose dexamethasone suppression test is also widely used and has its own pros and cons.
4. Imaging — abdominal ultrasound to assess the adrenal glands. Useful for distinguishing pituitary-dependent from adrenal-dependent disease.
5. In some cases referral for MRI of the pituitary, particularly when surgery or radiation therapy of a pituitary tumour is being considered.

Most cases are diagnosed and started on treatment in 1–3 visits over 2–4 weeks. Don't be surprised if your vet wants to confirm with a second test before committing to lifelong medication — the diagnosis isn't as black-and-white as conditions like diabetes.

Treatment options

Pituitary-dependent Cushing's (the common form)

The mainstay of UK treatment is the medication trilostane (Vetoryl), given orally once or twice daily for life. It blocks cortisol production at the adrenal gland. With dose adjustments based on regular blood monitoring, most dogs respond well within a few weeks — thirst settles, appetite normalises, energy improves, coat regrows.

Monitoring during treatment is important:

• An ACTH stimulation test or pre-pill cortisol every 2–4 weeks during the first few months while the dose is being titrated
• Every 3–6 months once stable
• More frequent if the dog becomes unwell or shows signs of overtreatment (lethargy, vomiting, diarrhoea, loss of appetite)

Undertreatment leaves the dog with persistent symptoms; overtreatment causes its own problems (Addisonian-like crisis). The right dose for any individual dog can take a few months to settle.

Adrenal-dependent Cushing's

For a single tumour in one adrenal, surgical removal can be curative when feasible — a major procedure typically referred to a specialist surgeon. Trilostane is also an option for medical management when surgery isn't appropriate (older dog, comorbidities, owner preference).

Pituitary surgery and radiation

In the UK, surgical removal of pituitary tumours (transsphenoidal hypophysectomy) is performed at a small number of referral centres and can be curative for pituitary-dependent disease. Radiation therapy is another option for large pituitary tumours causing neurological signs. These are specialist treatments reserved for selected cases.

Typical UK costs in 2026

• Initial diagnosis (consultation + bloods + ACTH stim): £300–£700
• Abdominal ultrasound: £200–£400
• Trilostane (varies by dog size): £60–£200/month
• Monitoring blood tests in first 3 months: £100–£200 per visit, every 2–4 weeks
• Quarterly to twice-yearly maintenance bloods: £100–£200 per visit
• Specialist referral for adrenalectomy or pituitary surgery: £5,000–£12,000+

Most lifetime insurance policies cover Cushing's as a long-term condition. Check the per-condition annual cap, whether ongoing trilostane is covered, and how monitoring tests count against the limit.