Primary
aldosteronism (PA) usually accompanies suppressed plasma
renin activity (PRA) through a negative feedback mechanism. While some cases of PA with unsuppressed PRA were reported, there have been no studies about the characteristics of PA with unsuppressed PRA; thus, these characteristics were examined herein. Nine patients with unsuppressed PRA and 86 patients with suppressed PRA were examined. All patients underwent segmental adrenal venous sampling (sAVS) and
adrenalectomy, and were pathologically confirmed to have
cytochrome P450 11B2 (CYP11B2)-positive
aldosterone-producing
adenoma according to international histopathology consensus criteria. Unsuppressed and suppressed PRA were defined as PRA levels of > 1.0 and ≤ 1.0 ng/mL/hr, respectively, in multiple blood samples obtained in the resting position. The unsuppressed PRA group had higher morning
cortisol levels (12.6 [8.5, 13.5] vs. 8.5 [7.1, 11.0] μg/dL, P = 0.03) and higher
cortisol levels after a 1 mg
dexamethasone suppression test (DST) (2.2 [1.6, 2.5] vs. 1.3 [1.0, 1.9] μ g/dL, P = 0.004) than the suppressed PRA group. The unsuppressed PRA group also showed higher
aldosterone levels on the non-surgical side during sAVS (P = 0.02 before
adrenocorticotropic hormone (
ACTH) stimulation, P = 0.002 after
ACTH stimulation), a higher intensity of
CYP17 expression in the resected adrenal gland (P = 0.02), and a lower clinical complete success rate 1 year after surgery (P = 0.04) compared with those in the suppressed PRA group. These findings suggest that PA should not be ruled out by unsuppressed PRA among patients with
hypertension, particularly when their
cortisol levels remain unsuppressed in the 1 mg DST. Meanwhile, it should be acknowledged that patients with unsuppressed PRA have higher
aldosterone levels on the non-surgical side, and a lower likelihood of postoperative complete clinical success is to be expected.