What Is Cushing's Disease in Dogs?

2. The three types of Cushing’s disease

Pituitary-dependent Hyperadrenocorticism (PDH)

This is the most common type, affecting 80-90% of dogs with Cushing’s disease. It’s caused by a tumor on the pituitary gland at the base of the brain, which makes the gland produce too much ACTH, a hormone that signals the adrenal glands to make more cortisol. This overproduction of ACTH leads to a continuous cycle of excessive cortisol release, causing the symptoms associated with Cushing’s disease to develop gradually over time.

Adrenal Tumor Hypercortisolism

This type affects about 15-20% of dogs with Cushing’s disease. It’s caused by a tumor on one of the adrenal glands, which are located near the kidneys. These tumors can be either benign or malignant. Benign tumors can sometimes be managed effectively with surgery, while malignant tumors pose a greater challenge, often requiring a combination of surgery and ongoing medical treatment to control the disease.

Iatrogenic Cushing’s Disease

This type is caused by the long-term use of steroids for treating other medical conditions. The body ends up with too much cortisol because of the medication. This form of Cushing's disease is often reversible if the use of steroid medications is carefully reduced or discontinued under veterinary supervision, but the process must be managed to avoid other complications.