Endocrine Abstracts

Adrenal vein sampling (AVS) is used to differentiate between unilateral and bilateral subtypes of primary aldosteronism (PA). However, AVS results may be misinterpreted due to a procedural artefact resulting in low aldosterone levels at the inferior vena cava (IVC), thus making an interpretation of aldosterone to renin ratios difficult. We investigated whether this artefact was due to patients’ being supine before and during AVS, given aldosterone varies with posture, and/or due to conducting AVS at midday, given aldosterone’s diurnal variation. We obtained peripheral samples of aldosterone and cortisol pre-AVS while patients were ambulatory, during AVS from the IVC while patients were supine, and post-AVS while patients were in an elevated bedrest position. We then analysed the variation of aldosterone with postural changes throughout the day and assessed the correlation between aldosterone and cortisol on the day of AVS. From 5 AVS procedures, the IVC aldosterone was low (<200 pmol/l) in three and below the limit of detection (≤60 pmol/l) in one. When examining aldosterone’s variation with posture in patients with PA, peripheral aldosterone showed non-significant reductions from pre-AVS to AVS (P=0.11) and from pre-AVS to post-AVS (P=0.19) and a non-significant increase from AVS to post-AVS (P=0.09). Assessment of aldosterone and cortisol’s relationship on the day of AVS revealed a mild positive correlation (r2=0.59; P=0.02). The decreases in aldosterone from pre-AVS to AVS suggests posture plays a major role. The correlation between aldosterone and cortisol on the day of AVS suggests diurnal variation likely also contributes to low IVC aldosterone during AVS. Overall, our preliminary findings indicate minimizing the time patients spend supine during AVS and shifting AVS timings from midday to morning may prevent suppression of aldosterone during AVS. Further collection of prospective data is necessary to confirm the significance of these findings.