Background: The normal cut-offs of screening and diagnostic tests for autonomous aldosterone (AAS) and cortisol (ACS) secretion are poorly defined, mainly due to the presence of adrenal adenomas among those who have served as controls and the stimulating effect of ACTH on aldosterone secretion.
Methods: We investigated cortisol and aldosterone secretion in 151 patients with benign cortical adrenal adenomas (BCAA) and in 119 healthy controls with a normal CT of adrenals. Tests for AAS were performed before and after dexamethasone suppression to eliminate the ACTH effect on aldosterone secretion. Performed tests: 1. ACTH-test (250 μg ACTH 1-24, IV) for cortisol, plasma active renin (PRC), aldosterone (PAC) and PAC/PRC ratios measurements at 0, 30 and 60 min. 2. Classical saline infusion test (SIT, 2 liters NaCl 0.9%/4 h, IV) for PRC, PAC and PAC/PRC ratios measurements, 3. LDDST (0.5 mg DEX/6hX24 h) for ACTH and cortisol measurements. 4. A further saline infusion test (POST-DEX-SIT) 2 h after the LDDST.
Results: Using ROC analysis the POST-LDDST cortisol levels (26.90 nmol/L), as well as the POST-DEX-SIT PAC (53.45 pmols/L) and POST-DEX-PAC/PRC (6.18 pmols/L/mU/L) achieved a 100% sensitivity and specificity. Using these new cut-offs the estimated prevalence of ACS and AAS among the BCAA-patients was 61.58% and 33.74% respectively, whereas simultaneous AAS and ACS was observed in 15.68% of the patients. Both systolic and diastolic blood pressure were significantly correlated with POST-DEX-SIT PAC/PRC ratio (P<0.003 and P<0.002 respectively) and PAC/PRC ratio at 60 min of ACTH-test (P<0.0003 and P<0.001 respectively) but not with the basal measurements.
Conclusions: With the newly defined normal cut-offs even mild forms of ACS and AAS were identified. As a consequence the estimated prevalence of ACS and AAS in BCAAs was found much higher than the reported previously, whereas a high prevalence of simultaneous cortisol and aldosterone secretion was identified for first time.