Endocrine Abstracts

Background: Aldosterone to renin ratio (ARR) is the gold standard for screening of primary aldosteronism (PA). However, the lower value of ARR cannot rule out the possibility of PA. In this study, we evaluated the change of plasma aldosterone concentration (PAC) in ACTH stimulation among hypertensive patients and explored whether it improved the sensitivity of ARR for detecting PA.

Method: Eighty-five patients with hypertension with plasma renin activity (PRA)<1.1 ng/ml/hr and PAC>50 pg/ml were enrolled for the ACTH stimulation test. The stimulation was performed by intravenous injection of 250 μg of ACTH to the patients after 30 min rest in the spine position. The blood sample was collected at 0, 30 and 60 min after the injection. Thirty-seven patients were suspected of PA by ARR>200 or PAC at 30 or 60 min after ACTH stimulation >240 pg/ml or having adrenal adenomas. The rest of 48 patients were classified into the non-PA group without confirmation (group A). PA suspected group was followed by confirmatory tests according to the Japanese guideline of PA diagnosis in 2009. Eight patients were excluded and re-categorized into the non-PA group with confirmation (group B) and 29 patients were classified into the PA group (group C).

Results: ΔPAC30 and ΔPAC60 were significantly higher in the group C (5.6±2.9, 3.2±1.6) than in the group A (2.2±1.0, 1.1±0.5) and group B (3.5±1.3, 2.0±0.9) (P<0.05). The ROC curve analysis demonstrated ARR0 of 233 (AUC=0.92, sensitivity=83%, specificity=98%), ARR30 of 392 (AUC=0.94, sensitivity=93%, specificity=89%) and ARR60 of 387 (AUC=0.96, sensitivity=93%, specificity=91%) as the optimum cut-off points.

Conclusion: These results indicated that ACTH amplified inappropriate aldosterone secretion. ARR after ACTH stimulation is more sensitive for detecting PA than that without the stimulation.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.