ESPE Abstracts (2014) 82 P-D-1-3-17

Aldosterone/Renin Ratio as Key Player in the Diagnosis of Primary Hypoaldosteronism in Newborns and Infants

Beate Rueckera, Mariarosaria Lang-Muritanoa, Katharina Spanausb, Maik Welzelc, Dagmar Lallemandd, Franziska Phan-Huge, Daniel Konrada, Claudia Katschniga, Paul-Martin Holterhusc & Eugen Schoenlea

aDepartment of Endocrinology/Diabetology, University Children’s Hospital Zurich, Zurich, Switzerland; bDepartment of Clinical Chemistry, University Hospital Zurich, Zurich, Switzerland; cDepartment of Endocrinology, University Children’s Hospital Kiel, Kiel, Germany; dDepartment of Endocrinology, Children’s Hospital St Gallen, St Gallen, Switzerland; eDepartment of Endocrinology, University Hospital Lausanne, Lausanne, Switzerland

Background: Primary hypoaldosteronism (PA) is a rare inborn disorder with life-threatening symptoms in newborns and infants due to an aldosterone synthase defect. As plasma aldosterone concentration (PAC) can remain in the normal range, interpretation of the laboratory findings could be difficult and might lead to delayed initiation of therapy.

Objective and Hypotheses: This study aims to show that PAC/PRC (plasma renin concentration) ratio can be used as a reliable diagnostic tool for PA in newborns and infants. Up to now this method is only validated to diagnose random conditions of disorders of the renin–angiotensin-aldosterone axis in adults.

Method: Ten patients with diagnosed PA were included. In 9/10 diagnosis was genetically confirmed by detecting pathogenic mutations in the CYP11B2 gene. The homozygous mutation T185I (8/10) and a compound heterozygous mutation with heterozygoty for T185I and for c.1398+1 G>A (1/10) were detected. In one patient the genetic result is pending. PACs and PRCs were available in 8/10. For those the PAC/PRC ratio was calculated in (pmol/l)/(mU/l). As patients were included from three different centres, the analytic methods differed. In order to enable a valid comparison of the values, PACs and PRCs were correlated to reference methods.

Results: In eight patients the PAC/PRC ratio was <1 (pmol/l)/(mU/l) (min: 0.0001–0.6538, mean: 0.1382). In one patient renin was noted as plasma renin activity (PRA). The PAC/PRA ratio was with 4.8 (pmol/l)/(ng/ml×h) also clearly decreased. In one patient no values for aldosterone and renin were available.

Conclusion: It was already shown in adults that a PAC/PRC ratio <1 (pmol/l)/(mU/l) and a PAC/PRA <28 (pmol/l)/(ng/ml×h) helps to identify patients with primary hypoaldosteronism. Due to our results this seems to be a very reliable screening tool in newborns and infants with aldosterone synthase deficiency as well. Thus we propose its introduction as a standard diagnostic tool.