Biomarkers in endometriosis: challenges and opportunities

Endometriosis is a debilitating gynecologic disease affecting millions of women across the world, with symptoms including dysmenorrhea, chronic pelvic pain, and infertility. Theorized to stem from the phenomenon of retrograde menstruation, the diagnosis of endometriosis is typically delayed by 8-10 years owing to misinterpretation of symptoms as common menstrual cramps in adolescent girls and young women. With increased incidence of endometriosis in young girls correlated with earlier menarche, the development of diagnostic biomarkers is imperative for diagnosing and treating women afflicted with endometriosis as early as we can. In the past few years, multiple reviews highlighted the list of potential diagnostic candidates in peritoneal fluid, blood, urine, and endometrial biopsies from endometriosis patients in different stages of disease and menstrual cycle. In this review, we explore the opportunities and challenges facing the field of diagnostic biomarkers for endometriosis. We highlight the importance of eutopic endometrium as a source of potential diagnostic biomarkers by looking at the expression levels of noncoding RNA in tissue as well as in blood. Finally, we discuss some of the challenges that hinder our efforts in validating candidate diagnostic biomarkers for endometriosis.