Endocrine Abstracts

Introduction: Primary hyperaldosteronism (PH) is characterized by autonomous adrenal aldosterone (A) hypersecretion. Unilateral adrenalectomy is the treatment of choice, when adrenal vein sampling (AVS) indicates lateralization of A secretion. To assure that each adrenal vein (AV) has been correctly sampled, cortisol levels in each adrenal vein must be higher than in the inferior vena cava. The adrenal gland cortisol/vena cava cortisol ratio is referred to as the selectivity index (SI). In most protocols, a SI ≥2 is considered an indication of correct AV catheterization. However, venous anatomic variants, modifying venous drainage, can dilute AV sample. As a result, cortisol levels in AV could be reduced in spite of correct catheterisation, without invalidating the aldosterone/cortisol ratio used to calculate the lateralization index. Androstenedione measurement has been proposed as an alternative to cortisol for calculation of the SI. The aim of the study was to evaluate the use of androstenedione values for SI calculation in AVS.

Materials and methods: Retrospective analysis. Thirty-three patients with a diagnosis of PA underwent consecutive AVS in a single general hospital over a 10-month period. A, cortisol and androstenedione serum levels were measured in the both AVs and in the inferior vena cava in all tests. AVS was performed early in the day, without ACTH infusion. Venous adrenal samples were consecutive, with a 6–10 minute delay between sampling of the right and left veins. Cortisol was measured by radioimmunoassay (DRG), androstenedione by competitive chemiluminescence immunoassay (IMMULITE 2000 XPi, Siemens).

Results: Table 1 shows the Selectivity Indices calculated using Cortisol or Androstenedione: Median [Interquartile range].

When using cortisol, 19/33 (57.57%) AVS presented SI≥2. An additional 7 patients had SI≥2 using androstenedione, for a total of 26/33 (78.78%) with SI≥2. Regression analysis. When comparing cortisol levels of cortisol-selective studies with androstenedione levels, right adrenal R²=0.86 (P<0.001) with left adrenal R²=0.64 (P< 0.001).

Conclusions: The calculation of the AVS selectivity index using androstenedione could be useful to ascertain whether adrenal veins have been correctly catheterized, in patients with low cortisol indices. In this series of patients, an androstenedione SI cut-off value ≥2 increased the number of selective AVS studies by 21.2%. The response of patients to AVS-based unilateral adrenalectomy when selectivity has been established by androstenedione must be evaluated before the use of androstenedione can be recommended to establish AVS selectivity.