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Eur J Clin Invest 2011; 41 (11): 1227-1236 Abstract Background Previous studies based on standard endocrine testing have generally shown a low prevalence of primary aldosteronism, a form of autonomous aldosterone secretion (AAS), in hypertensive individuals. The purpose of this case-control study was to evaluate whether use of appropriately defined controls and combined testing reveal previously undetected AAS in hypertensives. Materials and methods We investigated aldosterone secretion in 180 hypertensives with ( n = 44) and without ( n = 136) adrenal adenomas on computerized tomography (CT) and 72 matched nonhypertensive individuals with normal adrenal CT. Serum aldosterone and active renin were measured, and the aldosterone/active renin ratio was calculated before and after a modified fludrocortisone-suppression test (FST).In the latter, to eliminate any stimulatory effect of endogenous stress-induced adrenocorticotrophin hormone on aldosterone secretion, we administered 1 mg of dexamethasone on the last day of the classical FST fludrocortisone/dexamethasone suppression test (FDST). Results Using the 97·5 percentiles of serum aldosterone (74 pM L−1) and the aldosterone/renin ratio (32 pM L−1 mU−1 L−1) values obtained from the controls following the FDST, normal cut-off values indicative of adequate aldosterone suppression were established. Using the combination of these cut-offs, the estimated prevalence of AAS in patients with hypertension was 31%. Multiple linear regression analysis revealed a significant correlation between systolic and/or diastolic arterial blood pressure and the aldosterone value ( P < 0·0001 and P < 0·01, respectively) and/or the aldosterone/renin ratio ( P < 0·0001 and P < 0·01, respectively), which were obtained following the FDST. Conclusions By applying new cut-offs obtained following modification of standard testing, AAS is quite prevalent in hypertensive individuals and correlates highly with arterial blood pressure. This may have relevance for both the aetiology of the hypertension and its optimal therapy. [ABSTRACT FROM AUTHOR]