Longitudinal analysis of plasma renin concentration (PRC) in 112 patients with adrenal insufficiency at baseline and follow-up (median time between assessments = 433 days; range, 33–2082). Variation in PRC was defined as “increased” (>15% rise from baseline), “decreased” (>15% fall from baseline) or “no change” (<15% deviation from baseline). Longitudinal change in absolute PRC (a) and categorization of PRC change (b) in 80 patients with unchanged MC dose from baseline, 23 patients in whom MC dose was increased (c and d) and 9 patients with an decreased MC replacement dose (e and f).