Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease characterized by decreased daily activity and persistent fatigue after physical and/or cognitive exertion. Although ME/CFS affects both sexes, there is a higher preponderance of cases in women. However, endocrinological studies focused on evaluating this sex-related disparity are limited. In this scenario, the aim of this study was to measure 9 circulating steroid hormones (SHs) divided into mineralocorticoids (aldosterone), glucocorticoids (cortisol, corticosterone, 11-deoxycortisol, cortisone), androgens (androstenedione, testosterone), and progestins (progesterone, 17α-hydroxyprogesterone) in plasma samples from mild/moderate (ME/CFSmm; females, n=20; males, n=8), severely affected patients (ME/CFSsa; females, n=24; males, n=6), and healthy controls (HC, females, n=12; males, n=17) using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). After correction for multiple testing, we observed that circulating levels of 11-deoxycortisol, 17α-hydroxyprogesterone in females, and progesterone in males were significantly different between HC, ME/CFSmm and ME/CFSsa. Comparing two independent groups, we found that female ME/CFSsa had higher levels of 11-deoxycortisol (vs. HC and ME/CFSmm) and 17α-hydroxyprogesterone (vs. HC). In addition, female ME/CFSmm showed a significant increase in progesterone levels relative to HC. In contrast, we observed that male ME/CFSmm had lower circulating levels of cortisol and corticosterone, while progesterone levels were elevated compared to HC. In addition to these univariate analyses, our correlational and multivariate approaches identified differential associations between our study groups. Also, using two-component partial least squares discriminant analysis (PLS-DA), we were able to discriminate ME/CFS from HC with an accuracy of 0.712 and 0.846 for females and males, respectively. In conclusion, our findings not only suggest the potential value of including SHs in future studies aimed at improving stratification in ME/CFS, but also provide new perspectives to explore the clinical relevance of these SH-related differences within specific patient subgroups.
