Intra-individual variability in aldosterone levels is substantial.

In patients with resistant hypertension, establishing a diagnosis of primary aldosteronism can be challenging in primary care practice. One reason is the intra-individual variability in blood aldosterone levels.

Researchers examined this problem in a retrospective study of 216 Brazilian patients with hypertension, suppressed or low-normal plasma renin, and confirmed primary aldosteronism. All patients had two or more measurements of serum aldosterone and plasma renin (median, three measurements), done in the morning on different days. Key findings were as follows:

• intra-individual variability was substantial; for any cut-off chosen to identify serum aldosterone as elevated, many patients had at least one level above and one level below the cut-off
• at least one aldosterone level was below 416 pmol/L in 38% of patients, and at least two aldosterone levels were below that threshold in 20% of patients
• even at a lower cut-off of 277pmol/L (to maximise sensitivity), 14% of patients still had at least one level below that threshold
• variability in the aldosterone-renin ratio paralleled the variability in serum aldosterone
• 35% of patients in this cohort had normal potassium levels; their aldosterone levels were lower on average than aldosterone levels in hypokalaemic patients.

Comment: Recent research indicates that the prevalence of primary aldosteronism among patients with hypertension is higher than traditionally thought. This study reminds us to not necessarily dismiss primary aldosteronism when a single aldosterone level is reported as ‘normal.’ Particularly in patients with hypokalaemia or resistant hypertension, additional testing should be done to confirm or rule out the diagnosis.

Allan S. Brett, MD, Clinical Professor of Medicine, University of Colorado School of Medicine, Aurora, USA.

Maciel AAW, et al. Intra-individual variability of serum aldosterone and implications for primary aldosteronism screening. J Clin Endocrinol Metab 2023; 108: 1143-1153.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine.