Cushing's Disease

Also called: Hyperadrenocorticism, HAC, Cushing's syndrome

• Dogs
• Hormonal (endocrine)
• Senior

A condition of chronic excess cortisol. The most common natural forms are pituitary-dependent (a pituitary tumour driving the adrenal glands) and adrenal-dependent (an adrenal tumour). A further form is caused by long-term steroid medication (iatrogenic).

Signs to look for

• Increased thirst and urination
• Increased appetite
• A pot-bellied appearance
• Panting, hair loss, and thin skin
• Recurrent skin and bladder infections
• Muscle weakness and lethargy

How a vet diagnoses it

Clinical signs plus routine bloodwork and urinalysis, then specific hormone tests — the low-dose dexamethasone suppression test is the usual screening test, with the ACTH stimulation test and imaging also used. False positives are common when another illness is present, so testing is done thoughtfully.

Treatment

Trilostane is the main medication (mitotane is an alternative); surgery or radiotherapy in selected cases. Steroid-induced (iatrogenic) Cushing's is managed by carefully adjusting the steroid medication.

Monitoring at home

Lifelong monitoring with recheck bloodwork and ACTH stimulation testing to keep dosing appropriate. Affected dogs carry other risks (e.g. blood clots, high blood pressure, diabetes).

Who tends to get it

Middle-aged to older dogs. Pituitary-dependent disease is more common in small breeds; adrenal tumours tend to occur in larger dogs.

Sources

• Merck Veterinary Manual — Cushing Syndrome (Hyperadrenocorticism) in Animals
• ACVIM — Consensus Statement on Diagnosis of Canine Hyperadrenocorticism