[Cushing's syndrome. Recent findings]

Cushing's syndrome is presently divided into ACTH-dependent and ACTH-independent forms. Eighty percent of the former is caused by an ACTH-secreting pituitary adenoma (Cushing's disease), presently considered of monoclonal origin. Fifteen percent of the ACTH-dependent forms are due to ectopic secretion of ACTH and/or CRH by tumors. The ACTH-independent forms are due to adrenal tumors or are iatrogenic. A peculiar form of Cushing's syndrome is the nodular adrenal hyperplasia which may be ACTH-dependent or independent according to the stage of the disease. Definitely rare is the micronodular adrenal dysplasia, a form of ACTH-independent hypercortisolism which is part of a multi-tumoral syndrome (Carney's complex) and is attributed to circulating antibodies which bind to the ACTH receptors promoting adrenal growth and steroidogenesis. The diagnosis of Cushing's syndrome is firstly directed to ascertain the existence of hypercortisolism, then to establish its cause. However, the functional exploration of the hypothalamic-pituitary-adrenal axis on which the laboratory diagnosis is founded may provide misleading results in major depression, chronic ethylism, liver or renal failure, polycystic ovary syndrome as well as during therapy with antiepileptic drugs, rifampicin and estrogens. Furthermore, Cushing's syndrome may have an intermittent or cyclic pattern. Defining the cause of Cushing's syndrome may also be difficult due to the overlapping of clinical and laboratory findings in pituitary and ectopic ACTH hypersecretion.(ABSTRACT TRUNCATED AT 250 WORDS)