Nocturnal, Daytime, and Postural Changes of Plasma Aldosterone before and during Dexamethasone in Adenomatous and Idiopathic Aldosteronism

The relative importance of ACTH and the renin angiotensin system for control of aldosterone was studied in eight patients with adenomatous primary (APA) and four with idiopathic aldosteronism (IHA). Plasma aldosterone (PA) and cortisol (PC) were measured in blood collected during the night at 15-min intervals between 0500–0800 h by integrated sampling on day 1 and in casual samples during the daytime while patients were in the upright and in the supine position (days 1 and 2, at 1200, 1600, and 2000 h). PRA was measured in all daytime samples. On days 3, 4, and 5, 2 mg dexamethasone were given, and the same protocol for blood sampling was repeated on days 4 and 5. During the night, mean PA in IHA patients was markedly lower than that in APA patients. PA significantly correlated with PC in both groups. Dexamethasone reduced the mean nocturnal PA in both groups to equal proportions. In the daytime, the mean recumbent PA in IHA patients was also significantly lower than that in APA patients but was equal in ...