REN and hypertensive disorder: Circulating aldosterone levels are associated with reduced endothelial function (measured by flow‐mediated dilation) in the general population (Hannemann et al., 2011) and patients with chronic heart failure (Duprez et al., 1998), hyperaldosteronism (Nishizaka, Zaman, Green, Renfroe, & Calhoun, 2004) and low‐renin hypertension, with the latter shown to be due to impaired nitric oxide‐mediated vasodilation (Duffy et al., 2005).