Abnormal Responsiveness to Dexamethasone-Suppressed CRH Test in Patients With Bilateral Adrenal Incidentalomas.

The bilateral formation of nodules indicates that the pathogenesis of bilateral adrenal incidentalomas (AI) may differ from that of unilateral AI. A possible role of hypothalamo-pituitary-adrenal (HPA) axis dysregulation in their formation has not been investigated. The objective of the study was to evaluate the presence of altered feedback regulation of HPA axis in patients with bilateral AI. The dexamethasone (DEX) suppression-CRH test was used to assess ACTH and cortisol responses in controls and patients with unilateral and bilateral AI. The study was conducted at endocrine departments of two tertiary centers. We studied 24 controls and 39 patients with unilateral and 46 with bilateral AI. All subjects underwent standard low-dose dexamethasone suppression followed by iv bolus administration of human CRH (100 μg). Bilateral AI had higher levels of ACTH and cortisol after the DEX-CRH challenge compared with both controls (P < .01 for ACTH and P < .001 for cortisol) and unilateral AI (P < .01 for ACTH and cortisol). A positive response, defined as peak ACTH greater than 10 pg/mL at 15 and/or 30 minutes followed by a significant rise in cortisol levels, was noted in 41.3% of bilateral vs 2.6% in unilateral AI (P < .001). Bilateral responders did not differ from nonresponders in demographic or hormonal characteristics, but they had larger total adrenal size compared with nonresponders. A significant proportion of patients with bilateral AI demonstrate positive responses to the DEX-CRH test compared with unilateral AI, providing ground for potential involvement of HPA axis dysregulation in the pathogenesis, in at least a subgroup, of bilateral AI patients.