Endocrine Abstracts

In supine subjects aldosterone daily variations are determined by spontaneous PRA rhythmicity and ACTH secretory bursts. The aim of this study was to analyze diurnal and pulsatile aldosterone secretion in two patients with primary aldosteronism (PA): a 33-year-old woman with aldosterone producing adenoma (APA) and a 40-year-old woman with idiopathic adrenal hyperplasia (IAH). Blood samples were taken hourly during 24 hours at the time of the diagnosis and three months later, after tumour removal in the first case. Aldosterone was also analyzed after dexamethasone suppression in second case. Patients were supine except from 8 AM to 6 PM when they were allowed unrestricted ambulation. PRA levels were suppressed in both patients, but normal after tumour removal. In APA no circadian variations of aldosterone levels were registered before tumour removal. After that circadian variations were found with amplitude 0.074 nmol/l, period 12.25 h and maximum at 12.40 h. In patient with IHA aldosterone exhibited amplitude 0.148 and 0.297 nmol/l, period 8.67 and 15.59 h and maximum at 10.00 and 15.10 h respectively, but circadian rhythm was lost on dexamethasone. There was no correlation with PRA levels. Aldosteron pulsatile secretion was preserved in both patients: APA 6 and 8 pulses, 4.2 and 2.9 interpulse interval, 2.48 and 0.38 amplitude, 6.86 and 0.59 pulse mass before and after tumour removal; IAH 8 and 7 pulses, 3.14 and 3.67 interpulse interval, 0.79 and 0.99 amplitude, 1.22 and 1.76 pulse mass. We demonstrated that aldosterone pulsatile secretion is present in patents with PA. Mean serum aldosterone levels are increased due to higher pulse amplitude and concentrations between pulses. Reproducibility of aldosteron circadian rhythm existence is confirmed in IHA. The lost of aldosterone daily rhythmicity in PA due to aldosteronoma and IAH on dexamethasone may underline greater dependency on ACTH control.