Diagnosis of Cushing's Syndrome in the Modern Era.

Four challenges complicate the evaluation for Cushing syndrome. These challenges include increasing global prevalence of obesity and diabetes; increasing use of exogenous glucocorticoids, which cause a Cushing syndrome phenotype; the confusion caused by nonpathologic hypercortisolism not associated with Cushing syndrome, which may present with symptoms consistent with Cushing syndrome; and difficulty identifying pathologic hypercortisolism when it is extremely mild or cyclic or in renal failure, incidental adrenal masses, and pregnancy. Careful choice of screening tests, consideration of confounding conditions, and repeated testing when the results are ambiguous improve the accuracy of diagnosis.