Table 1.

Summary of key studies that have provided evidence for altered steroid biosynthesis and/or action in eutopic endometrium or endometriosis lesions from patients.

Title/topic	Methods	Results	References
Expression of ESR1 vs ESR2 in endometriosis lesions compared with endometrium	Fibroblasts isolated from endometrioma and endometrium, immunohistochemistry, evaluation of methylation status of ESR2 promoter	ESR2 overexpressed in lesions compared with ESR1; mechanism involving altered methylation	Xue et al. (2007)
Gene expression analysis of endometrium reveals progesterone resistance and candidate susceptibility genes in women with endometriosis	Endometrial tissue biopsies from 21 women with endometriosis and 16 women without, cycle stage determined. Affymetrix arrays+gene ontogeny	Phase-dependent changes in gene expression in both tissue sets. Patient samples – enrichment of genes involved in proliferation in early secretory phase dysregulation of P target genes in secretory phase	Burney et al. (2007)
Gene expression profile for ectopic vs eutopic endometrium provides new insights into endometriosis oncogenic potential	Paired samples of endometriomas and endometrium (12 women, luteal phase). Nimgen microarrays, validation of 20 genes, pathway analysis (DAVID)	Cluster-dependent modulation of HOX genes Altered cell cycle genes (suppressed?)	Borghese et al. (2008)
Prostaglandin E2 via SF-1 coordinately regulates transcription of steroidogenic genes necessary for oestrogen synthesis in endometriosis	Stromal cells isolated from wall of endometriomas (17) and endometrium (16), extra-ovarian tissue from differentgroup of women (13). RT-PCR steroid enzyme mRNAs, ChIP assays	StAR, P450scc, P450c17, P450arom are higher in ectopic samples. SF1 is high and binds promoter of StAR	Yilmaz and Bulun (2019)
Intra-tissue steroid profiling and enzyme analysis confirms differences in steroid metabolism in the endometrium and endometriosis lesions	RT-PCR analysis of enzymes in lesions vs endometrium, LC-MS/MS for direct measurement of steroid concentrations	Altered tissue steroid concentrations in endometriosis; altered expression of various steroidogenic enzymes HSD3B2 high CYP11A1 low	Huhtinen et al. (2012)