PTGS2 and endometriosis: Clinical observations also indicate that inflammatory mediators, such as cyclooxygenase-2 (COX-2), interleukin-1 beta (IL-1β), interleukin-8 (IL-8), tumor necrosis factor alpha (TNF-α), and prostaglandin E2 (PGE2), are significantly elevated in the peritoneal fluid of patients with endometriosis [19].