Night-day variations of renin-activity in primary aldosteronism

To detect changes in previously unmeasurable low renin activity plasma specimens of 20 patients with primary aldosteronism (12 with an unilateral adenoma and 8 with idiopathic bilateral adrenal hyperplasia), obtained at short term intervals between 20.00 and 8.00, were incubated over a prolonged period of 18 hours. 6 of 12 patients with an aldosterone producing adenoma (APA) and 3 of 8 patients with idiopathic bilateral adrenal hyperplasia (IAH) showed typical night-day variations of PRA with lower values before and higher values after midnight. 7 of these 9 patients with night-day rhythmicity of PRA simultaneously showed secretory episodes. In 2 patients (1 with APA, 1 with IAH) PRA was constantly undetectable (less than 0.2 ng/ml . 18 h) and in 2 patients with APA a fixed secretion of renin was observed. We failed to demonstrate typical night-day variations of PRA in 3 patients with APA and in 4 with IAH, although in 5 of these 7 patients secretory episodes of PRA were found. Our results show that different patterns of PRA curves may be observed both in patients with APA and IAH. Thus, analysis of PRA curves is of no value to differentiate patients with APA from those with IAH.