What is Cushing's syndrome?
Cushing's syndrome β also called hyperadrenocorticism (HAC) β is a chronic excess of cortisol, the body's main stress hormone, produced by the adrenal glands. It is one of the most common endocrine disorders in middle-aged and senior dogs (7β12 years). In 80β85 % of cases a small pituitary tumour over-stimulates the adrenals (pituitary-dependent HAC); in 15β20 % an adrenal tumour secretes cortisol autonomously.
Signs and symptoms
- Pot belly / pendulous abdomen β the most striking sign: cortisol redistributes fat and weakens abdominal muscles.
- Polydipsia and polyuria β drinking and urinating far more than usual.
- Polyphagia β intense, constant hunger.
- Symmetrical hair loss on flanks, belly and neck without itching.
- Thin, fragile, hyperpigmented skin; comedones; calcinosis cutis (calcium deposits in skin).
- Lethargy and exercise intolerance.
- Excessive panting.
- Muscle wasting and hind-leg weakness.
- Increased susceptibility to infections (urinary, skin, respiratory).
Predisposed breeds
Poodle (especially miniature), Dachshund, Boxer, Beagle, Boston Terrier and Yorkshire Terrier have higher prevalence, but any breed can be affected. Most dogs are over 6 years old at diagnosis.
Diagnosis
- Blood panel: markedly elevated alkaline phosphatase (ALP), hypercholesterolaemia, elevated ALT.
- Urine cortisol:creatinine ratio (UCCR): sensitive screening test; a normal result essentially rules out HAC.
- Low-dose dexamethasone suppression test (LDDST): the gold standard for confirming HAC.
- ACTH stimulation test: distinguishes spontaneous vs. iatrogenic HAC (caused by long-term steroid use).
- High-dose dexamethasone test (HDDST): helps differentiate pituitary vs. adrenal HAC.
- Abdominal ultrasound: assesses adrenal gland size and detects adrenal tumours.
Treatment
Pituitary-dependent HAC
- Trilostane (Vetoryl) β inhibits cortisol synthesis. First-choice treatment in Europe and the UK. Administered once or twice daily. Requires regular ACTH stimulation monitoring every 3β6 months.
- Mitotane (Lysodren) β destroys adrenal cortical tissue. Effective but carries higher risk of Addisonian crisis. Less used in Europe.
Adrenal tumour
Surgical adrenalectomy is potentially curative if there is no metastasis. High-risk surgery requiring specialist anaesthesia and surgical teams. If inoperable, trilostane controls symptoms.
Long-term monitoring
Regular check-ups and ACTH stimulation tests are essential once treatment starts. Trilostane overdose can precipitate an Addison-like crisis (hypoadrenocorticism) β a medical emergency. Owners must recognise the signs: sudden severe lethargy, vomiting, diarrhoea, collapse, and seek emergency care immediately.
With well-managed Cushing's, many dogs enjoy a good quality of life for years. Track cortisol results, medications and symptoms in Purzi to share a complete history with your vet at every check-up.