[Role of hormonal exploration in avoiding of the failures of anterior pituitary gland surgery in Cushing disease].

Patients with Cushing's disease are not cured by transsphenoidal microsurgery in about 30% of the cases. Beside the problem of invasive macroadenomas, these failures are due either to diagnostic errors, or to very small microadenomas that could no be found. Positive diagnosis of hypercortisolism is quite straightforward and the problem is sensitivity rather than specificity. Primary adrenocortical hypercortisolism should not be mistaken. Depression-related hypercortisolism can be difficult to distinguish from Cushing disease: most cases are recognized after clinical story and CRF stimulation test. Ectopic ACTH secretion by a carcinoid tumor represents at least 8% of ACTH-dependant hypercortisolism. It cannot be reliably distinguished from corticotroph microadenoma by either classical dynamic tests or anterior pituitary imaging. However measurements of ACTH in the inferior petrosal sinus under basal condition and CRF stimulation allow the diagnosis of central or peripheral ACTH secretion with a quasi 100% sensitivity and specificity. In contrast this technique is of poor help for the diagnosis of lateralization of corticotroph microadenomas, for which it gives erroneous results in 25 to 50% of the cases. Rapid intraoperative measurement of ACTH in peripituitary blood seems a more reliable approach. In our series it gave correct results in 11 out of 12 cases. In 1995 hormonal exploration of Cushing disease should limit the failures of anterior pituitary surgery to the cases of invasive macroadenomas that cannot be completely removed.