[Cushing syndrome: Physiopathology, etiology and principles of therapy].

The most frequent cause of Cushing's syndrome is iatrogenic, as Cushing's syndrome is the unavoidable consequence of long-term glucocorticoid treatment using more than 7.5 mg prednisone per day. The most frequent cause of endogenous Cushing's syndrome is Cushing's disease (CD), which is an ACTH dependent hypercortisolism linked to a pituitary corticotroph adenoma. This adenoma is often very small, its diagnosis may require bilateral inferior petrosal sinus sampling and the first line treatment of CD is transsphenoidal surgery by an expert neurosurgeon. The second line treatments include drugs that can act either on the pituitary adenoma or on adrenal steroidogenesis, pituitary radiotherapy or bilateral adrenalectomy. Ectopic ACTH dependent Cushing's syndrome is linked either to poorly differentiated endocrine tumors with a very poor prognosis, such as small cell lung cancer, or to well differentiated endocrine tumors, such as bronchial carcinoid tumors, which have a good prognosis when treated by surgery, but may be very difficult to localize. Adrenal Cushing's syndromes, which are independent of pituitary ACTH secretion, include adrenal cortex carcinoma, which requires abdominal surgery with extended adrenalectomy by an expert surgeon, adrenal adenoma which is treated by laparoscopic unilateral adrenalectomy and bilateral macronodular hyperplasia, whose surgical treatment may require unilateral or bilateral adrenalectomy. Treatment of Cushing's syndrome generally leads to spectacular clinical results, which must not hide the fact that the reversibility of some signs is actually incomplete. This underlines the need for a timely multidisciplinary management of the patients by an expert team.