ESPE Abstracts (2018) 89 P-P2-292

Aldosterone, Renin, Sodium and Potassium Excretion in Normotensive Prepubertal Children

Alejandro Martinez-Aguyoa, Helena Poggia, Carmen Campinob, Soledad Peredoc, René Baudrandb, Cristian Carvajalb, Ivonne D’Apremontd,e, Rosario Moored, Sandra Solarif, Fidel Allendef & Carlos Fardellab


aEndocrinology Unit, Division of Pediatrics, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; bEndocrinology Department, School of Medicine, Pontifica Universidad Católica de Chile, Santiago, Chile; cNephrology Unit, Division of Pediatrics, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; dDivision of Pediatrics, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; eComplejo Asistencial Sótero del Río, Santiago, Chile; fDepartment of Clinical Laboratories, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile


Introduction: Previous studies have demonstrated that hypertension may begin early in the life. Under physiological conditions, the Renin-Angiotensin-Aldosterone System (RAAS) is highly variable due to variations in salt intake and other factors, making it difficult to interpret results. We measured aldosterone and renin, and compared them with sodium and potassium excretion in a normotensive pre-pubertal population.

Methods: A cross-sectional study was performed in 40 healthy normotensive children (23 females; 5.2 to 8.9 years old). Office blood pressure (BP) was measured in a seated position using an oscillometric device, according to international recommendations. Normal BP was defined as the mean of 3 determinations lower than the 90th percentile using international references. Systolic and diastolic BP indexes (SBPi and DBPi) are expressed as observed BP/50th percentile BP. Morning plasma aldosterone and renin were measured by immunoassay (DiaSorin), also electrolytes in serum as well in urine collected after discarding the first morning sample were obtained. Sodium and potassium excretion was assessed by calculating: FENa (100×(urinary sodium × serum creatinine) ÷ (serum sodium×urinary creatinine)), TTKG (urinary potassium/plasma osmolality ÷ serum potassium/urinary osmolality) and SUSPPUP (serum sodium/urinary sodium ÷ serum potassium 2/urinary potassium).

Results: (median [3rd to 97th percentile]): The median age was 7.0 [5.2–8.8] years, and SBPi and DBPi were 1.02 [0.87–1.10] and 1.02 [0.82–1.20], respectively. Concentrations of aldosterone were 12.6 [3.3–48.1] ng/dL and for renin 35.1 [12.6–125.2] μUI/mL. As calculated, aldosterone/renin ratio was 0.38 [0.08–1.19] ng*mL/μUI*dl, FENa 0.34 [0.08–0.95] %, TTKG 8.28 [2.96-16.55], NaU/KU 1.15 [0.19–5.05] and SUSPPUP 6.37 [1.49–37.09] ((mmol L (−1))(−1). Pearson correlation (r) of aldosterone and renin to electrolytes derived ratios and their statistical significance (*=P < 0.05, **=P<0.01) are presented in the Table 1. Linear regression analysis showed the following results for SUSPPUP: Aldosterone = SUSPPUP * 1.092+6.7 (R2=0.66; P<0.001) and renin = SUSPPUP * 1.764+28.6 (R2=0.25; P=0.001).

Table 1
Pearson correlation (r)FENaTTKGNaU/KUSUSPPUP
Aldosterone−0.491**0.643**−0.557**0.811**
Renin−0.2540.459**−0.344*0.495**

Conclusion: In a normotensive pediatric population, renin and aldosterone concentrations were highly associated with SUSPPUP, an equation where small changes in potassium levels are better represented. SUSPPUP could be a complement for an adequate interpretation of RAAS. It is necessary to demonstrate if SUSPPUP in pediatrics subjects is also useful in RAAS related diseases. FONDECYT 1160836.