Cushing's syndrome (also called hypercortisolism or hyperadrenocorticism) is an hormonal disorder caused by high levels of cortisol in the blood from a variety of causes, including primary pituitary adenoma (known as Cushing's disease), primary adrenal hyperplasia or neoplasia, ectopic ACTH production (e.g., from a small cell lung cancer), and iatrogenic (steroid use).

Cushing's disease a common condition in older dogs, often mistaken for the aging process itself.