Objective: During the investigation of adrenal incidentalomas, it is important to accurately diagnose autonomous cortisol secretion (ACS) but the specificity of cortisol ≥50 nmol/L after overnight dexamethasone suppression (cortisolONDST) is low. Therefore, ACTH following overnight dexamethasone suppression (ACTHONDST) and cortisol following a 2-day dexamethasone suppression test (cortisol2-DAYDST) were examined as markers of HPA axis suppression during ONDST. Design: This cross-sectional study examined patients with adrenal incidentalomas and basal ACTH ≥ 2.0 pmol/L who underwent ONDST. Measurements: ACTHONDST/ACTH ratio (ACTH ratio) was calculated for all patients. To define cut-off levels for ACTHONDST and ACTH ratio as markers of HPA axis suppression, ROC curves were used to separate patients with cortisolONDST <50 and ≥50 nmol/L. Results: CortisolONDST was ≥50 nmol/L in 140 out of 373 patients. In patients with cortisolONDST <50 nmol/L, ACTHONDST was 0.28 pmol/L (<0.23–2.7). DHEAS was positively correlated to ACTHONDST, demonstrating a 9% increase with a doubling in ACTHONDST, p = 0.02. The best cut-off levels for ACTHONDST and ACTH ratio to detect cortisolONDST ≥50 nmol/L were ≥0.6 pmol/L and ≥18% respectively. These cut-off levels were tested on patients with cortisolONDST <50 nmol/L, considered to have adequate suppression (n = 233), and patients with reduction of ≥50 nmol/L from cortisolONDST to cortisol2-DAYDST, who were considered to have inadequate suppression (n = 16). ACTHONDST ≥0.6 pmol/L and ACTH ratio ≥18% had a sensitivity of 75% and 81% respectively, and a specificity of 78% and 85% respectively, for detecting patients with inadequate suppression. Conclusions: ACTHONDST and ACTH ratio can be markers of HPA axis suppression in the investigation of adrenal incidentalomas. CortisolONDST ≥50 nmol/L with ACTHONDST <0.6 pmol/L or ACTH ratio <18% should lead to the suspicion of ACS.
- Endokrinologi och diabetes