USE OF DESMOPRESSIN IN BILATERAL AND SIMULTANEOUS INFERIOR PETROSAL SINUS SAMPLING FOR DIFFERENTIAL-DIAGNOSIS OF ACTH-DEPENDENT CUSHINGS-SYNDROME

In a substantial proportion of patients with Cushing's syndrome, confl icting dynamic tests and the absence of radiological images make the d iagnosis of an ACTH-producing source difficult. In these circumstances , the role of bilateral and simultaneous inferior petrosal sinus sampl ing (IPSS) for ACTH determination already is well established, This me thod was used in 18 patients with Gushing's syndrome to establish the source of ACTH secretion, The diagnosis of Gushing's syndrome was conf irmed by elevated urinary cortisol excretion and resistance of serum c ortisol to dexa-methasone suppression (2 mg/day/orally), ACTH dependen cy was established by a positive response to desmopressin, metyrapone, and high-dose dexamethasone suppression (8 mg/day), IPSS was carried out before and after the administration of desmopressin (DDAVP 10 mu g IV), and the gradient between pe-trosal sinus and pe-tripheral venous ACTH levels was determined. Of 17 patients with evidence of Gushing's disease, 14 had a petrosal sinus to peripheral venous ACTH gradient g reater than or equal to 2.0 that increased dramatically after stimulat ion with desmopressin, 10 mu g IV. In two of three patients with a bas al gradient <2, stimulation with desmopressin increased the pe-trosal sinus to peripheral gradient, allowing the diagnosis of pituitary dise ase, Lateralization of the pituitary lesion by the interpetrosal sinus gradient was correct in only nine patients, A significant gradient wa s noted in two cases of corticotrope hyperplasia. IPSS with stimulatio n by DDAVP, like corticotropin-releasing hormone, can be used to in cr ease the central to peripheral gradient and to improve the diagnostic power of the procedure.