[Prevalence, etiology and clinical findings of Cushing's syndrome].

Endogenous Cushing's syndrome is a very rare entity, with an incidence of 2-4 cases per million inhabitants per year. Cases caused by ectopic ACTH secretion are under-diagnosed. Cushing's disease is the most frequent cause of endogenous Cushing's syndrome, which is 5 or 6 times more frequent than adrenal Cushing's syndrome, with an incidence of between 1.2 and 2.4 cases per million inhabitants per year. Cushing's disease is 3-8 times higher in women than in men. The frequency of adrenal tumors is 3 times higher in women, while that of Cushing's syndrome due to adrenal tumors is 3-5 times higher. Age at diagnosis of Cushing's syndrome varies according to the etiology. Most cases of Cushing's disease are due to a pituitary adenoma, although the tumor may not be visible on the available imaging techniques. ACTH-independent Cushing's syndrome is found in 20% of cases and is most frequently due to adenomas (10%) or adrenal carcinomas (8). Bilateral micronodular hyperplasia and macronodular hyperplasia are infrequent entities, representing less than 10% of all cases of ACTH-independent Cushing's syndrome. Both familial and sporadic forms exist: the familial form, or Carney complex, and ACTH-independent bilateral macronodular hyperplasia, in which the size of the adrenal glands is considerably enlarged. The signs and symptoms of Cushing's syndrome are a direct result of long-term exposure to excessive glucocorticoids. Most signs and symptoms are highly prevalent in the general population (hypertension, central obesity, diabetes mellitus or carbohydrate intolerance, osteoporosis, and characteristic phenotypical alterations).