CYP19A1 and endometriosis: STS mRNA was more expressed in relation to the others enzymes, in all sample groups analyzed, followed by HSD17B1 and finally by CYP19A1. ARO protein expression was higher among groups, followed by STS and HSD17B1. We detected differences between CYP19A1:STS ratios, CYP19A1:HSD17B1 (gene expression), ARO:STS, and ARO:HSD17B1 (protein expression) in different sites of endometriosis.