Plasma renin measurements are unrelated to mineralocorticoid replacement dose in patients with primary adrenal insufficiency.

CONTEXT No consensus exists for optimization of mineralocorticoid therapy in patients with primary adrenal insufficiency. OBJECTIVE To explore the relationship between mineralocorticoid replacement dose, plasma renin concentration (PRC) and clinically important variables to determine which are most helpful in guiding mineralocorticoid dose titration in primary adrenal insufficiency. DESIGN Observational, retrospective, longitudinal analysis. PATIENTS 280 patients (with 984 clinical visits and plasma renin measurements) with primary adrenal insufficiency recruited from local databases and the international congenital adrenal hyperplasia (CAH) registry (www.i-cah.org). Thirty-seven patients were excluded from the final analysis due to incomplete assessment. Data from 204 patients with salt-wasting CAH (SW-CAH) (149 adults and 55 children) and 39 adult patients with Addison's disease (AD) were analysed. MAIN OUTCOME MEASURES PRC, electrolytes, blood pressure (BP) and anthropometric parameters were used to predict their utility in optimizing MC replacement dose. RESULTS PRC was low, normal or high in 19%, 36% and 44% of patients, respectively, with wide variability in mineralocorticoid dose and PRC. Univariate analysis demonstrated a direct positive relationship between mineralocorticoid dose and PRC in adults and children. There was no relationship between mineralocorticoid dose and BP in adults, while BP increased with increasing mineralocorticoid dose in children. Using multiple regression modelling, sodium was the only measurement that predicted PRC in adults. Longitudinally, the change in mineralocorticoid dose was able to predict potassium, but not BP or PRC. CONCLUSIONS The relationship between mineralocorticoid dose and PRC is complex and this may reflect variability in sampling with respect to posture, timing of last mineralocorticoid dose, adherence and concomitant medications. Our data suggests that mineralocorticoid titration should not primarily be based only on PRC normalization, but also on clinical parameters as BP and electrolyte concentration