Recurrence of Cushing's disease preceded by the reappearance of ACTH and cortisol responses to desmopressin test

At present no single test is considered of absolute value in identifying patients successfully operated for Cushing's disease who are at risk for recurrence. The present report describes the first two patients in whom ACTH/cortisol abnormal responses to desmopressin disappeared after cure and then clearly reappeared during long-term follow-up several months before the clinical and hormonal features of hypercortisolism became manifest. The case histories of 2 young women are reported. The diagnosis of Cushing's disease was made on the basis of clinical features and standard hormonal criteria. Both patients, showing abnormal ACTH/ cortisol rises after desmopressin test, underwent pituitary adenomectomy by transsphenoidal surgery and after operation plasma ACTH and serum cortisol levels were 0.2 and 0.4 pmol/l and 56 and 32 nmol/l, respectively. During the follow-up both patients underwent desmopressin (10 μg iv), ovine CRH (1 μg/kg iv) and 1 mg dexamethasone tests at 1, 6, 12, 24 months after surgery. In these two cases the ACTH/cortisol response to desmopressin normalized following pituitary adenomectomy, concomitantly with the normalization of all the other clinical and hormonal parameters. Subsequently abnormal rises after the synthetic AVP analogue administration appeared: paradoxical ACTH/cortisol increments after desmopressin occurred 24 and 6 months before any other hormonal or clinical sign of recurrence of hypercortisolism. As desmopressin may be able to stimulate ACTH/cortisol release in Cushing's disease, but not in normal subjects, we suggest that it can have a role in early identifying successfully operated Cushing's patients at risk for recurrence.