Gas chromatography–mass spectrometry profiling of steroids in urine of patients with acute intermittent porphyria

Abstract

ObjectiveAcute intermittent porphyria (AIP) is an autosomal dominant disease that results from a deficiency of hydroxymethylbilane synthase, the third enzyme of the heme biosynthetic pathway. AIP carriers may present acute neurovisceral attacks with hepatic overproduction of heme-precursors. In some patients, remission of the acute symptoms leads to long-term hepatic metabolic abnormalities. In this study, gas chromatography–mass spectrometry (GC/MS) was used to investigate urinary steroid metabolome of AIP patients. Design and methodsSteroid profiling in urine was performed in a group of AIP patients with biochemically active disease (n=22) and healthy controls (n=20). Five asymptomatic AIP family carriers were also studied. Commonly used ratios for the evaluation of disturbances in the steroid metabolism were calculated. ResultsWe found that etiocholanolone/androsterone and tetrahydrocortisol/5α-tetrahydrocortisol (THF/5α-THF) metabolic ratios were significantly increased in the urine of AIP patients compared to controls (2.3±0.3 vs 0.8±0.1; p<0.001 and 2.9±0.7 vs 0.9±0.1; p<0.01). The (THF+5α-THF)/tetrahydrocortisone ratio was reduced among the AIP patients (p<0.01). Quantification of the steroid absolute concentrations showed that these variations were due to a decrease of the 5α metabolites. Other ratios, like cortisol/cortisone and 6β-hydroxycortisol/cortisol in the free steroid fraction did not show differences between patients and controls. All ratios were normal among the family carriers. ConclusionA significant number of AIP patients present a basal decrease of steroid 5α-reductase activity in the liver. The deficiency may be related to malnutrition and hepatic energy misbalance associated with active AIP. Urinary steroid profiling by GC/MS may be a valuable tool to assess hepatic metabolome in AIP.