Endocrine Abstracts

Introduction: Adrenal Venous Sampling (AVS) is considered the gold standard to identify surgically treatable primary aldosteronism (PA) subtypes. Current guidelines suggest using plasma cortisol concentrations to confirm successful adrenal vein (AV) cannulation and lateralisation, but cortisol co-secretion by adrenal adenomas can lead to diagnostic misinterpretation. Plasma metanephrines (MN) have a half-life of 3 to 6 min and are not affected by cortisol co-secretion, and therefore may offer a more precise and sensitive approach when used as an alternative analyte to cortisol to diagnose unilateral PA.

Aim: This study aims to demonstrate superiority of measuring MN over cortisol in patients with PA and mild autonomous cortisol co-secretion.

Methodology: We studied 132 patients undergoing unstimulated AVS in a tertiary referral centre carried out by a single operator between January 2018 to May 2023. Plasma samples for MN were collected from both AV and PV. Cannulation success was determined by using AV/PV cortisol >2 or AV/PV MN >12. Unilateral disease was confirmed by an aldosterone/cortisol ratio >2, aldosterone/MN ratio >5 and contralateral suppression by a ratio below 0.5 of that in PV.

Results: The cannulation success rate was 98%. Among 132 cases, 73 underwent overnight dexamethasone suppression testing, which identified 14 patients with mild autonomous cortisol co-secretion (cortisol >50 nmol/l [53–201] post dexamethasone) and low or suppressed baseline ACTH. AVS results were discordant in 4 out of 14 patients with mild autonomous cortisol co-secretion as well as in one patient with post-dexamethasone cortisol of 36 nmol/l, with aldosterone/cortisol suggesting bilateral disease and aldosterone/MN indicating unilateral disease. Four out of those 5 patients with discordant results underwent unilateral adrenalectomy and histological analysis confirmed an adrenocortical adenoma in all cases. One patient opted for medical therapy. All surgically treated patients achieved complete clinical and biochemical remission according to PASO criteria.

Conclusion: This study provides a further important addition to the current literature demonstrating superiority of aldosterone/MN over aldosterone/cortisol to distinguish unilateral from bilateral disease in patients with PA and cortisol co-secretion undergoing unstimulated AVS.