Hyperadrenocorticism in Dogs

Abstract

This chapter discusses the pathogenesis, classical signs, diagnosis, and treatment for hyperadrenocorticism (HAC) in dogs. The clinical signs of HAC result from chronically elevated serum cortisol concentrations. More than 80% of dogs with HAC have pituitary-dependent disease due to an adrenocorticotropic hormone (ACTH)-secreting adenoma; approximately 80% originate in the adenohypophysis and 20% in the intermediate lobe. Older, small breed dogs are predisposed to spontaneous HAC. Tests for spontaneous HAC are divided into screening tests, meant to determine if HAC is present, and differentiating tests, designed to ascertain whether the disease is pituitary-or adrenal-based. Selegiline inhibits the enzyme monoamine oxidase B and, as a result, increases hypothalamic dopamine concentrations, which, in turn, inhibit ACTH secretion from the intermediate lobe of the pituitary. Selegiline is effective in at most 20% of cases of pituitary-dependent HAC.