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 rationalization 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 recognized in PA. Intermittent PA should be recognized 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 hypokalemia, adrenal adenoma visible), but with negative initial testing, should be followed with serial ARR measurements and subsequent careful timing of confirmatory or lateralization tests to maximize the chances of being in an active PA phase.
