Compared to normal endometrium, endometriosis samples showed elevated levels of heme-degradation-pathway-associated genes: Hmox1 (encoding HO-1), BLVR-A and BLVR-B, and hemopexin (Hx) as well as haptoglobin (Hp), a hemoglobin scavenger (Figure 1A–D). This evidence concerns the gene HMOX1 and endometriosis.