INFERIOR PETROSAL SINUS AVP IN PATIENTS WITH CUSHINGS-SYNDROME

OBJECTIVE In both normal volunteers and patients with Gushing's diseas e, one dominant inferior petrosal sinus (IFS) contains higher concentr ations of AVP and ACTH than the contralateral (non-dominant) IFS, but ovine corticotrophin-releasing hormone (oCRH)-stimulated AVP in the pe trosal sinuses is greater in Gushing's disease than in normal voluntee rs. To distinguish whether greater oGRH-releasable AVP might be specif ically related to the presence of a pituitary corticotrophinoma, or be due to hypercortisolism per se, we compared IFS AVP in patients with Gushing's disease with those of patients with other causes of Gushing' s syndrome. PATIENTS Twenty-three patients with Gushing's disease, 16 patients with the syndrome of ectopic ACTH and seven patients with Gus hing's syndrome of adrenal origin, MEASUREMENTS AVP and ACTH, measured both before and 3, 5 and 10 minutes after oCRH in the petrosal sinuse s, and in a peripheral vein. RESULTS In all three groups, AVP concentr ations were lateralized such that most of the AVP was found in one, do minant IFS. oCRH significantly increased IFS ACTH only in patients wit h Gushing's disease (P < 0.001), whereas it significantly increased do minant IFS AVP levels in all three patient groups (P < 0.01). However, neither dominant nor nondominant IPS AVP (basal or oCRH-stimulated) w ere significantly different among patients with Gushing's disease, ect opic ACTH or Gushing's syndrome of adrenal origin. Basal and oCRH-stim ulated IFS AVP were negatively correlated with urine free cortisol. CO NCLUSIONS Inferior petrosal sinus AVP levels are similar in ail forms of Gushing's syndrome, and thus the higher inferior petrosal sinus AVP levels in patients with Gushing's disease compared with normal volunt eers are unlikely to be related specifically to the presence of the pi tuitary corticotrophinoma. While AVP may play a role in pituitary cort icotroph tumourigenesis or may be secreted by some pituitary corticotr oph tumours, the observation that CRH-stimulated inferior petrosal sin us AVP levels are higher in Gushing's disease than in normal volunteer s appears most likely to be related to the low endogenous CRH revels i nduced by hypercortisolism, rather than a consequence of Gushing's dis ease itself. We hypothesize that low endogenous CRH leads to increased sensitivity of central nervous system CRH receptors to exogenous CRH, and thus to greater ovine CRH-stimulated AVP.