Endocrine Abstracts

Primary hyperaldosteronism is now recognised as the most frequent underlying cause of hypertension. We recruited 94 patients (age (mean±S.D.) 56±11 years) with hypertension from primary care in order to study the role of corticosteroid hormone action in this cohort. Random, blood pressure (BP), plasma renin activity (PRA) and aldosterone (Aldo) was measured both on and off antihypertensive medication. In addition, a 24 h ambulatory blood pressure (ABP) was recorded and a 24 h urine was collected for analysis of steroid hormone metabolites by gas chromatography/mass spectrometry (GC/MS). In seven patients (7%) BP off antihypertensive medication was found to be normal (mean 24 h ABP<125/80 mmHg) suggesting white coat hypertension as the underlying cause. Four patients (4%) showed suppressed PRA and elevated Aldo in keeping with primary hyperaldosteronism as the underlying cause. Mean BP on medication was 150±27 / 85±14 mmHg and did not change after stopping antihypertensive medication (151±20 / 86±11; P=n.s.), despite a significant fall in PRA from 4.1±9.9 nmol/l per h on treatment to 1.0±1.1 off all BP lowering agents. Erect Aldo was significantly higher than supine (133±182 vs 119±141 pmol/l, P<0.05). Furthermore, Aldo both erect and supine was positively correlated with diastolic (r=0.322, r=0.329; both P=0.003) but not systolic 24 h ABP. This was underpinned by a strong correlation of tetrahydro-Aldo (main urinary metabolite of aldosterone) excretion with diastolic BP on 24 h ABP (r=0.37, P<0.001). However, by contrast, PRA both erect and supine was negatively correlated with systolic (r=−0.295, r=−0.307; both P<0.01) but not diastolic BP. In conclusion, our data in a primary care hypertensive population suggest that 7% of patients may not need antihypertensive treatment and that 4% have underlying primary hyperaldosteronism. Furthermore, aldosterone levels are correlated with diastolic blood pressure whereas fluid overload reflected by low PRA is a determinant of systolic blood pressure.