Endocrine Abstracts

Differential diagnosis between bilateral adrenal hyperplasia (BAH) and aldosterone producing adenoma (APA) in aldosteronism remains challenging in many cases due to the high prevalence of incidentalomas during imaging techniques, the limited sensitivity of orthostatic testing and the technical difficulties of adrenal vein sampling (AVS).

We investigated circadian variation in salivary aldosterone (SA) in patients with APA (n=22) and BAH (n=20). In 12 APA patients, we also compared plasma aldosterone (PLA) during orthostatic testing (4 h) to diurnal changes in SA. Interfering medication was discontinued before sampling (mineralocorticoid receptor antagonists 4 weeks; ACE inhibitors, AT2, beta-blockers, 1 week). Patients underwent MRI/CT scan and APA was defined by successful AVS and/or cure after operation. Paired saliva samples were collected between 0800–1200 and 2000–2400 h. SA was measured using an in-house fluorometric assay, salivary cortisol by luminescence immunoassay (IBL, Hamburg).

Overall, mean (±S.E.M.) SA in APAs decreased from morning (146±17 pg/ml) to evening (92±13pg/ml, P=0.015), while in BAHs levels remained unchanged or increased (morning: 94±16 pg/ml; evening: 107±20 pg/ml (P=0.75). In the APA group, SA decreased in 18 patients (81.8%), was unchanged in one, and increased in three (13.6%). In 12 of these APA patients, PLA during posture testing was also available. PLA decreased in five, was unchanged in one and increased in six cases following posture. In these 12 patients SA decreased in 10 and increased only in two between morning and evening. Cortisol decreased diurnally in both groups as expected, excluding the influence of stress on evening aldosterone levels.

Compared to the 4-hour posture test, which shows increases in PLA in a significant number of APAs, the long-term diurnal decrease monitored by SA presents a more constant finding. Although a direct comparison between posture testing and SA measurements in patients with BAH is pending, our preliminary data suggest that SA could be a supporting tool in discrimination between BAH and APA.