Hyperadrenocorticism (Cushing’s Syndrome)

Cushing’s syndrome, or hyperadrenocorticism, is a common hormonal disorder affecting dogs, especially older and small breeds.

Research Authors


Cushing’s syndrome in dogs, caused by excessive cortisol production, can be either pituitary-dependent (PDH) or adrenal-dependent (ADH). Symptoms include increased thirst and urination, thinning fur, and muscle weakness. Diagnosis requires various tests, including hormone tests and an abdominal ultrasound. PDH is typically treated with medication, while ADH can be treated with surgery. The prognosis for dogs with PDH is generally good with proper treatment, while dogs with smaller adrenal tumours tend to have better outcomes post-surgery.

Cushing’s syndrome occurs when one or both adrenal glands produce too much cortisol, a stress hormone. There are two types of Cushing’s syndrome:

  1. Pituitary-dependent hyperadrenocorticism (PDH): This is the most common form and is caused by a small growth on the pituitary gland in the brain.
  2. Adrenal-dependent hyperadrenocorticism (ADH): Caused by a growth on one of the adrenal glands.



Picture of a dog with Cushing's syndrome.
Picture of a dog with Cushing's syndrome.

When the body produces too much cortisol, dogs may exhibit various signs such as increased thirst and urination, urinary incontinence, increased appetite, panting, fur loss, thin skin, pot-bellied appearance and muscle weakness. Cushing’s syndrome can also increase the risk of diabetes, gallbladder disease, strokes, high blood pressure, and secondary infections.

How is Cushing’s Syndrome diagnosed? 

Diagnosing Cushing’s syndrome involves having consistent symptoms and examination findings, alongside positive hormone test results. Since no single test can confirm the disease, a vet usually uses a combination of the following tests:

  • Urine cortisol-creatinine ratio
  • Low-dose dexamethasone suppression test
  • ACTH stimulation test

An abdominal ultrasound is often used to check adrenal gland size and shape.

How is Cushing’s Syndrome treated?  

Dogs with PDH are typically treated with a medication called trilostane (Vetoryl), which is usually given twice daily with food. It helps reduce cortisol levels. Regular follow-up check-ups and blood tests are necessary to monitor cortisol levels and ensure they don’t drop too low.

For dogs with ADH, surgery to remove the affected adrenal gland (adrenalectomy) is often recommended.

What is the prognosis for dogs with Cushing’s Syndrome?  

Most dogs with pituitary-dependent hyperadrenocorticism (PDH) do well with treatment and typically live out their normal lifespan. However, in some cases, the pituitary tumour in the brain can grow, causing problems. This occurs in about 10-25% of dogs with PDH, from months to years after diagnosis, and can result in serious neurological symptoms.

In cases of adrenal-dependent hyperadrenocorticism (ADH), surgery to remove the affected adrenal gland (adrenalectomy) can cure the condition, as long as the tumour can be completely removed and there is no metastasis. This surgery typically eliminates the need for lifelong medication. Dogs with adrenal tumours smaller than 3 cm tend to have a significantly better survival rate after surgery compared to those with tumours 3 cm or larger.

The internal medicine team at ARC has extensive experience treating dogs with Cushing’s syndrome and takes great satisfaction in seeing the positive impact of good management on their quality of life.