Cushing’s Disease

Cushing’s syndrome (CS) results from prolonged exposure of tissues to excess of glucocorticoids. After Harvey Cushing’ s initial report in the early 20th century (1), CS has been etiologically subdivided into adenocorticotropin hormone (ACTH)-independent (nonpituitary) or ACTH-dependent (2–4). Endogenous CS is rare, with an overall incidence of approx two to four new cases per million of population per year. ACTH-dependent CS accounts for approx 85% of endogenous cases. In the majority of these cases (80%), the cause is autonomous pituitary ACTH secretion and is referred to as Cushing’s disease (CD). In the remaining 20%, the ACTH secretion source is ectopic. CD has a female to male preponderance (8/1), whereas the ectopic ACTH syndrome is more common in men (3/1). Ectopic corticotropin-releasing hormone (CRH) production causing CS has also been described in approx 11 cases (5–7). In this chapter, we focus on the diagnosis and treatment of CD which generally presents between the second and sixth decades of life, with a peak incidence at age 35 yr (2).