Endocrine Abstracts

Background: Primary aldosteronism (PA) accounts for 5–10% of all patients with hypertension, and an even greater proportion of those with refractory hypertension. Accurate assessment of PA is important both for rationalisation of medical therapy and to identify those patients with unilateral disease who may benefit from surgery. Single timepoint testing may miss patients with intermittent (‘cyclical/periodic’) disease, a phenomenon seen in other endocrine hypersecretory syndromes, but not commonly recognised in PA.

Methods: Retrospective analysis of all patients diagnosed with PA in our centre (2013–2018) identified those who had discordant confirmatory tests for PA, with an initial suppressed saline infusion test (SIT) followed by a result consistent with PA. Clinical (including BP and potential confounding medications) and biochemical (serum potassium, plasma renin, plasma aldosterone) data were then reviewed for these patients.

Results: Three patients, for whom clinical suspicion of PA was high, demonstrated normal aldosterone suppression on an initial SIT with subsequent non-suppressed second SIT confirming PA. Confounding medications were excluded as reasons for the discrepancy. All three had marked variability in aldosterone levels with time, while renin remained <10 mU/L. The aldosterone:renin ratio (ARR) was also variably suggestive of PA with time. Blood pressure variability did not correlate with aldosterone levels and was not predictive for a positive ARR or SIT result.

Conclusion: Intermittent PA should be recognised as a clinical entity. This may lead to false negative exclusion of PA in some patients and resultant failure to offer appropriate management. We suggest that patients with a high pre-test probability for PA (e.g. young onset or refractory hypertension, unprovoked hypokalaemia, adrenal adenoma visible), but with negative initial testing, should be followed with serial ARR measurements and subsequent careful timing of confirmatory or lateralisation tests to maximise the chances of being in an active PA phase.