The renin-angiotensin-aldosterone system (RAAS) is a key regulator of blood volume. Because this system leads to an increase in plasma volume through sodium and water retention, one might therefore expect an increase in the components of the RAAS to be seen in response to the low blood volume in POTS.
In this study, the concentrations Ang I, Ang II, Plasma Renin Activity (PRA), and Ang-(1-7) were measured in patients with POTS and controls.
We found that the plasma concentration of Angiotensin (Ang) II was elevated in POTS compared to controls while both plasma renin activity (PRA) and aldosterone were lower in POTS than controls.