INFERIOR PETROSAL SINUS ARGININE-VASOPRESSIN CONCENTRATIONS IN NORMALVOLUNTEERS AND PATIENTS WITH CUSHINGS-DISEASE

In patients with Cushing's disease (CD), basal inferior petrosal sinus arginine vasopressin (AVP) concentrations are greater than peripheral levels and are further increased by the administration of CRH. AVP ha s an interpetrosal sinus gradient similar to that for ACTH, leading to the hypotheses that petrosal sinus AVP might either be derived from t he corticotroph adenoma or be important for adenoma formation. To dete rmine whether petrosal sinus AVP is truly increased in patients with C D, we compared inferior petrosal sinus and peripheral venous AVP and A CTH levels in 23 patients with CD and 9 healthy volunteers before and after iv ovine CRH. In both groups, AVP and ACTH showed interpetrosal lateralization, such that greater levels of both hormones were found a t each time point in a single dominant petrosal sinus. When both hormo nes exhibited lateralization (an intersinus gradient >1.5), ACTH and A VP always lateralized together. In patients with CD, the ACTH interpet rosal sinus lateralization correctly identified the side of the pituit ary containing the tumor in 75% of evaluable patients, whereas the AVP interpetrosal sinus lateralization identified 63% (P=NS). Ovine CRH s timulated AVP in both the dominant and nondominant petrosal sinuses in patients with CD. Although basal AVP in the dominant petrosal sinus w as not significantly different in patients with CD and normal voluntee rs (144+/-85 vs. 13.0+/-4.3 pmol/L; P= 0.058), dominant petrosal sinus AVP was significantly elevated in patients with CD compared to normal volunteers at 3 min (269+/-122 vs. 45.1+/-30.0 pmol/L; P <0.05) and 5 min (315+/-120 vs. 40.2+/-23.6 pmol/L; P <0.05) after ovine CRH admin istration. Peripheral venous AVP levels were similar in all groups. We conclude that lateralization of AVP secretion occurs in both patients with CD and normal volunteers, but there is greater CRH-stimulated AV P secretion in the inferior petrosal sinuses of patients with CD.