Clinical and biochemical characteristics of normotensive patients with primary aldosteronism: a comparison with hypertensive cases.

Objective: It is unknown why some patients with biochemical evidence of primary aldosteronism (PA) do not develop hypertension. We aimed to compare clinical and biochemical characteristics of normotensive and hypertensive patients with PA.

Design And Patients: Retrospective comparison of 10 normotensive and 168 hypertensive patients with PA for office or ambulatory blood pressure, serum potassium, plasma aldosterone and renin concentrations; the aldosterone:renin ratio, and tumour size. Comparison of initial hormonal pattern and drop in blood pressure following adrenalectomy in five normotensive and nine hypertensive patients matched for age, sex and body mass index.

Results: The 10 normotensive patients were women and presented with hypokalemia or an adrenal mass. Age, plasma aldosterone and renin concentrations were similar in normotensive and hypertensive cases, but kalemia and body mass index were significantly lower in the normotensive patients. Mean tumour diameter was larger in the normotensive patients than in the hypertensive matched patients with an adenoma (P < 0.01). In normotensive patients, diastolic blood pressure and upright aldosterone correlated negatively with kalemia. Blood pressure was lowered similarly after adrenalectomy in five normotensive PA patients and in their matched hypertensive counterparts. Aldosterone synthase expression was detected in four out of five adrenal tumours.

Conclusions: Blood pressure may be normal in patients with well-documented PA. The occurrence of hypokalemia, despite a normal blood pressure profile, suggests that protective mechanisms against hypertension are present in normotensive patients.