Cushing's Disease Management in Dogs: Deep Welfare Guide
Pathophysiology and Types
Hyperadrenocorticism (HAC/Cushing's disease) results from chronic excess cortisol. In 85% of cases, a pituitary adenoma causes excessive ACTH secretion (pituitary-dependent HAC/PDH). In 15%, an adrenal tumour directly secretes excess cortisol (adrenal-dependent HAC). Iatrogenic HAC from prolonged corticosteroid administration is also important. Each type has different treatment implications. Excess cortisol causes widespread metabolic and immune effects with significant welfare impact.
Clinical Signs and Welfare Impact
Classic signs include: PU/PD (excessive drinking and urination, causing house-training accidents and disturbing sleep); polyphagia (insatiable hunger, causing persistent food-seeking behaviour); pot-bellied appearance; muscle weakness (difficulty rising, reduced exercise tolerance); alopecia (bilateral symmetric hair loss); thin fragile skin; susceptibility to infection (UTI, skin infection); and calcinosis cutis (calcium deposits in skin, causing pain). The combination causes significant chronic welfare compromise.
Diagnosis
Diagnosis requires a combination of clinical signs and diagnostic tests. Screening tests include urine cortisol:creatinine ratio (UCCR), low-dose dexamethasone suppression test (LDDST), and ACTH stimulation test. No single test is 100% sensitive and specific; clinical correlation is essential. Differentiating PDH from adrenal tumour uses high-dose dexamethasone suppression test, abdominal ultrasound, and endogenous ACTH measurement. Computed tomography or MRI identifies pituitary macroadenomas and adrenal masses.
Medical Treatment and Monitoring
Trilostane (Vetoryl) is the most widely used treatment for both PDH and adrenal-dependent HAC in the UK. It inhibits cortisol synthesis. Regular monitoring (ACTH stimulation test 4 weeks after starting treatment or dose change, then every 3-6 months) ensures adequate control without over-suppression (adrenal crisis risk). Mitotane (o,p'DDD) is an older alternative. Adrenal tumours may be treated surgically (adrenalectomy) by specialist centres.
Quality of Life During Treatment
Well-controlled HAC leads to significant welfare improvement: PU/PD, polyphagia, and lethargy resolve; skin and coat improve; muscle strength returns. Owners typically notice dramatic quality of life improvement within weeks of achieving good control. Monitoring must be ongoing: any signs of adrenal insufficiency (weakness, lethargy, vomiting, anorexia) require urgent veterinary assessment and potential dose reduction. Careful client education about monitoring and recognising problems is essential for long-term welfare.