Plasma renin activity in essential hypertension (a critical approach to its significance)

A study of the frequency distribution of plasma renin activity (PRA) in 123 patients with essential hypertension (EH) produced no evidence of a distinct subpopulation with low renin levels, whether the samples were taken from supine or upright patients. Applying an arbitraty classification criterion, however, low PRA levels were found in 30.1% of patients. There were no significant differences in mean blood pressure, 24-h sodium excretion, and age when groups with low, normal or high PRA levels were compared. The incidence of PRA hyporesponsiveness was similar in the three groups of patients, but increased with age. In the female there was a preponderance of low PRA levels. It is concluded that EH with low PRA levels is not a separate diagnostic entity and, when PRA is low in a hypertensive subject, the possible effects of age, blood pressure, and sex ought to be taken into account before other causes of low PRA are postulated.