The role of renin, fludrocortisone, and hypertension in early childhood in patients with congenital adrenal...

To assess plasma renin levels, fludrocortisone dosing, and their relationships with electrolytes, blood pressure, and early growth in children with 21-hydroxylase deficiency (21OHD).

Retrospective single-centre longitudinal cohort study.

Patients born 2013-2022 and followed until age 3 years were included. Serial plasma renin, fludrocortisone dose, sodium chloride supplementation, electrolytes, and blood pressure were extracted from clinical records. Fludrocortisone trajectories and repeated-measures associations were analysed using mixed-effects models. Plasma renin was categorized as below, within, or above the assay reference range. Growth at 1 and 3 years was assessed as height SD score relative to target height.

Twenty-eight children were included. Fludrocortisone dosing peaked around 3 months (estimated mean 130 µg/day, 95% CI: 115-144) and declined to a plateau after 1 year (84 µg/day, 95% CI: 72-96). Higher renin levels were associated with lower sodium (approximately 139.7 vs 136.9 mmol/L) and higher potassium (4.09 vs 4.81 mmol/L). Suppressed renin levels were associated with the highest predicted probability of hypertension. Renin levels did not affect linear growth.

Renin suppression in early childhood is associated with increased hypertension risk, whereas higher renin was not associated with growth or electrolyte abnormalities. These findings emphasize the importance of avoiding mineralocorticoid overtreatment and monitoring blood pressure carefully.