Gas chromatographic-mass spectrometric analysis of urinary glycyrrhetinic acid: An aid in diagnosing liquorice abuse

Abstract

Objectives. Liquorice abuse can lead to severe clinical complications, caused by its active compound 18β-glycyrrhetinic acid (18βGA). 18βGA inhibits dehydrogenase activity of 11β-hydroxysteroid dehydrogenase (11βHSD). This enzyme catalyses the interconversion between cortisol and cortisone and normally protects the mineralocorticoid receptor from being activated by cortisol. Diagnosing liquorice abuse can be notoriously difficult. The aim of our study was to develop an accurate and clinically applicable 18βGA urinary assay. Design. We developed a urinary 18βGA assay based on gas chromatography and mass spectrometry (GCMS) with sufficient sensitivity to detect 18βGA at low concentrations. The assay was validated in four volunteers consuming different amounts of liquorice. We applied its use in two patients with hypokalaemic hypertension and suppressed plasma renin activity and serum aldosterone, who were suspected of liquorice abuse. Results. The detection limit for 18βGA of the GC assay was 10 μg L-1, which was lowered to 3 μg L-1 by subsequent application of MS. In all volunteers, urinary 18βGA was detected during liquorice intake. Urinary 18βGA remained detectable until 5 days after stopping continued liquorice intake and until at least 51 h after ingestion of a single large amount. Urinary 18βGA was demonstrated in both patients, establishing a diagnosis of liquorice abuse. One patient showed changes in urinary cortisol metabolites, consistent with 11βHSD inhibition. Changes in cortisol metabolites were less pronounced in the other patient. Conclusion. Liquorice abuse can result in hypokalaemic hypertension with prolonged suppression of plasma renin activity and aldosterone concentration. This is caused by 18βGA-mediated inhibition of 11βHSD, resulting in activation of the renal mineralocorticoid receptor by cortisol. Urinary 18βGA measurement by GCMS is a useful aid in establishing liquorice abuse.