Mineralocorticoid treatment in adrenal insufficiency

Context: Fludrocortisone (FC) is the mineralocorticoid (MC) replacement treatment for patients with primary adrenal insufficiency (PAI). Objective: To explore the dose of FC treatment and its relationship with glucocorticoid therapy, sodium, potassium and renin levels. Design: longitudinal study. Setting: monocentric cohort. Patients: Data of 193 patients with PAI (130 autoimmune) were collected during baseline (T0), intermediate (T1) and last follow-up visit (T2, respectively after 38 and 35 months). Main Outcome Measure: Utility of endocrine and clinical parameters to titrate FC dose. Results: FC dose (50-75 μg/daily) was stable in the follow-up in half patients. The MC activity of FC was dose-dependent: we observed a positive linear correlation between FC dose and sodium (r= 0.132) and negative linear correlation between FC and potassium (r= -0.162) or renin (r= -0.131, all p <0.01). An overall reduction in the FC dose was observed at T2 in the group with longer follow-up (>60 months, p <0.05). Higher doses of FC were observed in patients with low-normal renin, especially in autoimmune PAI (86 vs 65 μg/daily, p <0.05). On the contrary, reduced sodium and increased potassium levels were observed in patients with high renin at T2. The number of cardiovascular events (15 in the whole cohort) was similar in patients sorted by renin levels or FC dose. Conclusions: low-doses of FC are sufficient in most patients with PAI and can be further reduced in long-term follow-up. Renin and electrolytes are marker of MC activity: they should be routinely evaluated and used to titrate FC treatment.