PGR and endometriosis: While the cycle stage at induction may have minor impacts on tissue attachment, the cycle stage at necropsy is more important to control as hormone status (see Supplementary File S1: EPHect-EM-Homologous SOP 8) impacts expression of genes and proteins in endometriosis lesions (i.e. progesterone receptor (PGR), matrix metalloproteinases (MMPs), lactoferrin (LTF), etc.)(Burns et al., 2012).