The non-steroidal STS inhibitor STX64 also referred as Irosustat was the first to enter the clinical phase in postmenopausal women with breast cancer while steroidal inhibitor (E1-3-O-sulfamate, EMATE) together with progestin norethindrone acetate has been studied in endometriosis patients (Pohl et al., 2014). Here, STS is linked to endometriosis.