Hyperadreocorticism (Cushing's disease)

Hyperadrenocorticism (Cushing’s disease) is a relatively common endocrine disease of dogs but is rare in cats.

Aetiology

1. Excessive endogenous cortisol production
   • pituitary tumour (85% of cases) producing excessive adrenocorticotrophic hormone (ACTH) or
   • an adrenal tumour (15% of cases) producing excessive cortisol
2. Iatrogenic administration of exogenous glucocorticoids (iatrogenic hyperadrenocorticism).

Clinical signs
Hyperadrenocorticism is a slowly progressive disease with signs that vary in severity depending on the duration and degree of cortisol excess.

Clinical signs are similar to diabetes mellitus:

• polyuria
• polydipsia
• polyphagia

In addition dogs frequently have a pot-bellied appearance and alopecia or other skin and/or coat changes. Diabetes mellitus may develop secondary to hyperadrenocorticism, due to insulin resistance caused by cortisol excess.

Treatment
Hyperadrenocorticism can be treated medically or surgically. Concurrent diabetes mellitus requires insulin treatment.