Hyperadrenocorticism: the disease, diagnostics, and treatment for dogs

Hyperadrenocorticism (HAC), or Cushing's disease, is one of the most commonly diagnosed endocrinopathies in dogs (Herrtage and Ramsey, 2012), having been found in approximately 0.1% of the general canine population (Hill et al 2005). The condition results in excessive glucocorticoid production by the adrenal cortex of the adrenal glands. It is this chronically increased production of glucocorticoids that contributes to the negative effects on the patient's body. Because veterinary nurses play a vital roles in the diagnosis of HAC, it is important that they be able to identify the clinical signs of the disease, properly perform diagnostic tests, and understand the general treatment options available in order to achieve excellent client communication.

The axis controlling glucocorticoid release is initiated by the release of corticotropin-releasing hormone (CRH) from the hypothalamus. The CRH in turn stimulates the anterior pituitary gland to produce adrenocorticotropic hormone (ACTH). The ACTH then travels systemically to the cortex of both adrenal glands to synthesise and secrete cortisol (a glucocorticoid). The cortisol levels in the blood negatively feedback on the hypothalamus and pituitary to decrease the synthesis and release of CRH and ACTH (Figure 1).