Primary aldosteronism in normokalemic patients with adrenal incidentalomas

Since primary aldosteronism has been reported in asymptomatic incidental adrenal masses (adrenal incidentalomas, AI), the aim of our study was to detect primary aldosteronism in normokalemic patients with AI and to verify whether a raised plasma aldosterone (ALD)/plasma renin activity (PRA) ratio may be useful for diagnosis.

One-hundred and twenty-five normokalemic patients with solid AI (90 hypertensives and 35 normotensives) and 82 essential hypertensives (EH) were studied. Upright ALD and PRA determination was performed in all cases while patients with abnormal ALD/PRA ratios were submitted to confirmatory tests (saline infusion and captopril tests) for diagnosis of primary aldosteronism.

ALD and PRA were measured by specific radioimmunoassays.

PRA values in AI hypertensives (1.05+/-0.13 ng/ml/h) were lower than in AI normotensives (1.14+/-0.14 ng/ml/h, P<0.05) and in EH (1.68+/-0.15 ng/ml/h, P<0.0001). The ALD/PRA ratio in AI hypertensives (46.4+/-5.1) was higher than in AI normotensives (30.7+/-5.8, P<0.03) and in EH (33.2+/-3.5). Four patients with EH and 2 AI normotensive patients had elevated ALD/PRA ratios but normal responses to the suppressive tests, thus excluding diagnosis of primary aldosteronism. Eight patients with AI and hypertension had a high ALD/PRA ratio, and 7 of these were further studied: in 5 patients diagnosis of primary aldosteronism was well-established by dynamic tests, adrenal vein sampling or by surgery.

Primary aldosteronism in normokalemic patients with incidentally discovered adrenal masses was detected in 4 of all cases and in at least 5.5% of those with hypertension. Consequently, these patients, particularly if hypertensive, need to be routinely studied to exclude this hormonal disease. Evaluation of the ALD/PRA ratio seems to be a simple and reliable test for diagnosis.