Plasma Pituitary Prohormones and Pituitary Adenoma Size in Cushing’s Disease

Background: Hyperadrenocorticism in dogs is among the three most common endocrinopathies of dogs. Approximately 85% of dogs with spontaneous hyperadrenocorticism have pituitary-dependent hyperadrenocorticism (PDH). Pituitarydependent hyperadrenocorticism is due to an excessive secretion of adrenocorticotropic hormone (ACTH), usually by a pituitary microadenoma. However, up to 30% of PDH cases have macroadenomas. Medical treatment to suppress adrenocortical function can be effective treatment for PDH caused by microadenomas, but the medical management of PDH from macroadenomas is much less satisfactory. Yet, without computed tomography (CT) or magnetic resonance (MR) imaging, the size of pituitary tumors antemortem can only be speculated. There is preliminary evidence that the ratio of circulating precursors to ACTH (proopiomelanocortin and pro-ACTH) may differ between microadenomas and macroadenomas. Objectives: The purpose of this study was to investigate the relationship between plasma proopiomelanocortin (POMC)/pro-ACTH and the size of pituitary tumors in dogs with PDH.