Epidemiology of Cushing's syndrome.

Overt Cushing's syndrome is a rare disorder with an annual incidence of 2-3/million of which benign adrenal adenomas account for 0.6/million. The female:male ratio is 3:1. Preliminary data indicate a high proportion of subclinical Cushing's syndrome in certain risk populations such as patients with type 2 diabetes or osteoporosis. The clinical implications of these observations are presently unclear. Surgery remains first line treatment for overt disease and initial cure or remission is obtained in 65-85% of patients with Cushing's disease. Late recurrences, however, occur in up to 20% and the risk does not seem to plateau even after 20 years of follow-up. A 2- to 3-fold increase in mortality is observed in most studies, and this excess mortality seems confined to patients in whom initial cure was not obtained. Cushing's syndrome continues to pose diagnostic and therapeutic challenges and life-long follow-up is mandatory.