What is Cushing’s Disease or hyperadrenocorticism?

The release of steroids from the adrenal glands is regulated by the hormones released from the pituitary gland. The hormone released from the pituitary gland is called ACTH. Hyperadrenocorticism or Cushing’s Disease is a disease in which there is excessive production of glucocorticoids (steroids), by
the adrenal gland.

What causes hyperadrenocorticism?

There are three causes for hyperadrenocorticism:

1. Pituitary Dependent Hyperadrenocorticism (PDH)

In this situation, the pituitary gland is inappropriately producing too much ACTH. This causes an over-stimulation of the adrenal gland and the result is excessive cortisol production.

2. Adrenal Dependent Hyperadrenocorticism (ADH)

In this case, a functional adrenal tumor is present that is overproducing steroids.

3. Drug-induced Hyperadrenocorticism (Iatrogenic Cushing’s)

Glucocorticoids are used to treat a variety of medical problems. Long-term use of these drugs can result in clinical signs of hyperadrenocorticism.

What are common clinical signs associated with hyperadrenocorticism?

The clinical signs associated with hyperadrenocorticism develop due to excessive cortisol concentrations. These signs include the following:

1. Increased volume of urine (polyuria).
2. Increased water consumption (polydipsia).
3. Increased appetite (polyphagia).
4. Abdominal enlargement.
5. Skin abnormalities (hair loss, poor healing, easy bruising, increased pigment).
6. Testicular atrophy (males) and failure to cycle (females).
7. Difficulty breathing (shortness of breath and excessive panting).

How is hyperadrenocorticism diagnosed?

To confirm the diagnosis of hyperadrenocorticism, your veterinarian will want to run either a Low Dose Dexamethasone Suppression Test (LDDS) and/or an ACTH Stimulation Test. These tests involve
blood sampling and an injection of either ACTH or Dexamethasone (a steroid). Your dog will have to remain in the hospital for the day while these tests are being performed. Once the diagnosis of hyperadrenocorticism is confirmed, your veterinarian will want to determine the cause. The test that
is most commonly used is the High Dose Dexamethasone Supression Test. Additional diagnostic tests such as abdominal radiographs and ultrasound may also be necessary.

What is the treatment for hyporadrenocorticism?

Pituitary Dependent Hyperadrenocorticism: The recommended treatment for PDH is drug therapy with Lysodren or Trilostane. Lysodren will selectively destroy the areas of your dog’s adrenal gland that actively produce cortisol. Trilostane selectively blocks production of cortisol and other hormone products of the adrenal gland. With either drug, it will be necessary to monitor your dog’s appetite and attitude and watch for vomiting and diarrhea during treatment. Treatment with Lysodren or Trilostane is lifelong.

Adrenal Dependent Hyperadrenocorticism: The recommended treatment for ADH is surgical excision of the tumor. If surgical excision is not possible, Lysodren may also be effective.

Iatrogenic Hyperadrenocorticism: The recommended treatment for Iatrogenic Cushing’s is to gradually discontinue or decrease the doses of glucocorticoid administration.