Figure 3b-13: Crooke’s hyaline change in non-neoplastic corticotroph cells in response to hypercortisolaemia. The physiological response of normal corticotrophs to exposure of excess cortisol (of any source, neoplastic or iatrogenic) is downregulation of ACTH synthesis and development of hyaline, cytokeratin-rich perinuclear rings: Crooke’s hyaline degeneration (named after the English endocrinologist Arthur Carleton Crooke).