Changes in glycosylation have been reported in endometriosis such as altered glycosylation of plasma glycoproteins in secretory phase endometrial tissues from women with advanced endometriosis compared to controls, and aberrant glycosylation and expression of endometriosis-associated peritoneal haptoglobin, alterations in sialylation on endometrial cells and altered glycosylation on all serum glycoproteins and serum IgG of endometriosis patients1,15–17. Here, HP is linked to endometriosis.