Cushing Syndrome

Cushing syndrome is a condition with protean manifestations that are caused by chronic exposure to excess glucocorticoids. Treatment with supraphysiologic doses of glucocorticoids is the most common cause. Pathologic hypercortisolism may result from autonomous adrenal production or as a result of the action of excessive adrenocorticotropic hormone (ACTH) production by a tumor, which stimulates adrenal cortisol production. Primary adrenal forms include unilateral adenoma or carcinoma or, rarely, bilateral hyperplasia and/or nodules. This chapter covers the epidemiology, etiology, pathophysiology, and diagnosis of Cushing syndrome. Clinical manifestations, physical examination findings, and laboratory tests, including tests of the blood and other body fluids, imaging studies, and biopsy, are discussed. The differential diagnosis, treatment options, complications, and prognosis are described. Tables outline clinical features and causes of Cushing syndrome, abnormalities associated with primary adrenal causes of Cushing syndrome, diagnostic accuracy of screening tests, endogenous hypercortisolism without Cushing syndrome, and medical therapy for Cushing syndrome. Figures illustrate the causes of Cushing syndrome and a comparison of the hypothalamic-pituitary-adrenal axis in patients with ACTH-dependent Cushing syndrome and those with pseudo–Cushing syndrome. Algorithms show the evaluation of possible Cushing syndrome and evaluation of the causes of Cushing syndrome. Second-line treatments for Cushing syndrome when surgery fails or is not possible are also detailed. This chapter contains 5 figures, 7 tables, 50 references.