The Diurnal Rhythm of Plasma Aldosterone, Plasma Renin Activity, Plasma Cortisol and Serum Growth Hormone and Subnormal Responsiveness of Aldosterone to Angiotensin-II in the Patients with Normotensive Acromegaly

The diurnal rhythm of plasma aldosterone concentration (PA), plasma renin activity (PRA), plasma cortisol (PC) and serum growth hormone (GH) were examined in 5 cases of normotensive acromegaly and the results were compared with the observations in normal subjects. Moreover, the response of PA to angiotensin-II infusion was studied in 6 cases of normotensive acromegaly. A normal diurnal rhythm with the lowest values in the evening or midnight and the highest values in the morning was observed in 3 of 5 cases in PA and 3 of 4 cases in PC. On the other hand, no apparent rhythm of GH was observed in any cases and that of PRA in 4 of 5 cases. Although there was a significant positive correlation between PA and PC, no significant correlation was demonstrated between PA and PRA. The response of PA to angiotensin-II fusion was significantly suppressed in normotensive acromegaly as compared to the normal subjects in spite of normal levels of PRA except for 1 case. The above observations were interpreted to suggest that the aldosterone regulation system is slightly altered in a certain number of patients with normotensive acromegaly in contrast to the normal subjects in which PRA is the main contributing factor. The low PA and suppressed response of PA toangiotensin-II infusion may suggest the defective action of angiotensin-II infusion on the adrenal gland.