The desmopressin test as a predictive factor of outcome after pituitary surgery for Cushing's disease

Taking advantage of the over-expression of V3 receptors in adenomatous corticotroph cells, we evaluated the response to the vasopressin agonist desmopressin in 22 patients operated on for Cushing's disease, with a mean follow-up of 4.5 years.

Twenty-two patients (17 women) operated on for Cushing's disease with a follow-up >2 years (median, 48; range, 24-141 months) underwent one desmopressin test (10 microg i.v. bolus) 3-6 months postoperatively. Twelve were in remission (R group), five had immediate failure (IF) after surgery and five had late recurrence (LR).

Both ACTH and cortisol peaks after desmopressin were significantly lower in the R group than in the LR group (P=0.003 and P=0.013 respectively). The receiver operator characteristic curve method defined an ACTH peak threshold > or =22 pg/ml or ACTH rise > or =35%; cortisol peak > or =350 nmol/l or cortisol rise > or =14%. None of twelve patients in remission had ACTH or cortisol peaks above these thresholds vs three of five patients from the LR group and five of five in the IF group.

On the basis of ACTH or cortisol peaks respectively, the desmopressin test was predictive of a later recurrence with a positive predictive value of 100% or 80% respectively, and a negative predictive value of 92%. Sensitivity and specificity were 80% and 100% respectively based on ACTH peak, and 80% and 92% respectively based on cortisol peak.

In this first long-term study, a marked response of ACTH or cortisol to desmopressin was predictive of a later recurrence with good specificity and sensitivity.