BACKGROUND: Inhaled corticosteroids (ICS) are frequently prescribed medications for asthma symptoms, but higher doses can increase risks of adrenal insufficiency through suppression of endogenous cortisol production. Understanding which patients may be at increased risk for developing adrenal suppression related to ICS use may help providers improve treatment regimens for asthma patients
however, the mechanisms underlying ICS-related adrenal insufficiency have not been clarified. OBJECTIVE: This study identifies metabolite signatures and biochemical pathways associated with ICS-related adrenal insufficiency in asthma patients. METHODS: Global metabolite profiling (metabolomics) was integrated with electronic medical records data including the development of adrenal suppression, in two independent asthma cohorts. The discovery cohort, Pharmacogenomics of Adrenal Suppression with Inhaled Corticosteroids (PhASIC), included 711 adult asthma patients on ICS. Untargeted metabolomic profiling identified 1,397 metabolites, of which 810 were selected for further analysis. Using plasma cortisol as a biomarker for adrenal status (outcome), linear regression models were implemented to identify associations between metabolites and plasma cortisol, adjusted for potential confounders. Metabolite associations were validated in an additional 575 patients on ICS. Pathway and network analyses were performed using bioinformatic approaches to identify altered metabolic pathways related to the outcome. RESULTS: Of 810 endogenous metabolites, 12 demonstrated significant associations with adrenal insufficiency after correction for multiple comparisons. In the validation cohort, three of these 12 replicated, including two steroid metabolites (tetrahydrocortisol glucuronide and tetrahydrocortisol glucuronide (5)) and homocitrulline. Pathway and network analyses revealed alterations in biochemical pathways related to the metabolism of steroids, bile acids, urea cycle and long-chain polyunsaturated fatty acids. CONCLUSIONS: We have identified specific metabolites within steroid and non-steroid metabolic pathways that are associated with adrenal insufficiency with ICS use.