ECTOPIC ACTH PRODUCTION BY A BRONCHIAL CARCINOID-TUMOR RESPONSIVE TO DESMOPRESSIN IN-VIVO AND IN-VITRO

A desmopressin-induced ACTH increase has been recently suggested to be specific for pituitary-dependent Gushing's disease, We present the ca se of a 47-year-old woman with Cushing's syndrome due to ectopic ACTH production by a bronchial carcinoid, While CRH failed to induce an ACT H or cortisol response, intravenous administration of desmopressin led to a 47% increase in serum ACTH and a 42% increase in serum cortisol concentration, After surgical removal of the tumour, the desmopressin response became negative, In vitro, ACTH production by tumour cells ob tained at surgery was also stimulated by desmopressin but not by CRH. Additional receptor mRNA expression studies using RT-PCR revealed expr ession of both V2 and V3 vasopressin receptor subtypes in the carcinoi d tumour at a level comparable to that recently described in pituitary corticotroph adenomas, This case illustrates that ACTH stimulation by desmopressin is not specific for pituitary-dependent Gushing's syndro me as vasopressin receptor subtypes known to interact with desmopressi n may also be found in ectopic tumours producing ACTH.