Decreased plasma prorenin levels in primary aldosteronism: potential diagnostic implications

Primary aldosteronism could exert a negative feedback on prorenin secretion, of possibly different magnitude, whether it is related to an aldosterone-producing adenoma (APA) or an idiopathic hyperaldosteronism (IHA). The objectives of this study were to evaluate the level of prorenin in three subgroups: APA, IHA, and essential hypertension; and the performance of the aldosterone-to-prorenin ratio (APR) for the diagnosis of an APA.

Seven hundred and forty-six hypertensive patients with a standardized work-up, including a prorenin measurement, were considered. Ninety-six patients without neutral treatment and 38 patients with other forms of secondary hypertension were excluded. APA and IHA were categorized according to computed tomography scan, adrenal venous sampling, pathological analysis and improvement of hypertension after surgery.

Thirty-five patients had a diagnosis of APA, 57 of IHA and 504 of essential hypertension. Prorenin was lower in APA and IHA than in essential hypertension (32.9, 40.4 and 50.3  pg/ml, respectively; P < 0.001). APR was higher in patients with APA and IHA than in those with essential hypertension (24.0, 11.8, and 4.0  pmol/l per pg/ml, respectively; P < 0.001). The APR was more discriminant than the aldosterone-to-renin ratio to identify APA compared to IHA (area under the receiver operating curve at 0.750 and 0.639, respectively; P = 0.04). The optimal cut-off values were 22  pmol/l per pg/ml for APR (sensitivity 57.0%, specificity 93.0%) and 440  pmol/l per pg/ml for aldosterone-to-renin ratio (sensitivity 54.3%, specificity 82.5%).

Primary aldosteronism and particularly its most caricatural form, that is APA, seems associated with a lower level of prorenin than essential hypertension. The APR could be included in the diagnostic strategy of APA.