Endometriosis belongs to the most frequent non-malignantdiseases in women during childbearing years [1]. Thedisease depends on a complex interaction of immunologic,genetic, hormonal and environmental factors often leadingto pelvic pain with dysmenorrhoea, dyspareunia anddyschezia [2, 3]. In the peritoneal cavity of affected women,chemoattraction of macrophages accompanied by immunecell infiltration could be detected [4]. The symptoms ofendometriosis are also a product of the local inflammatoryresponse, e.g. tumour necrosis factor alpha and glycodelincorrelated positively with the level of menstrual pain in theperitoneal fluid of affected patients [5]. Endometriosis is anoestrogen-dependent disease and established treatmentstrategies (temporarily) suppress ovarian oestrogen produc-tion with known side effects like perimenopausal symp-toms. A myriad of possible points of application forprogestogens have been postulated. Beside reduced serumoestrogen levels leading to suppressed gonadotropin re-lease, progestogens cause decidualization in eutopic andectopic endometrium, inhibit angiogenesis by suppressingplasminogen activator activity and decrease intraperitonealinflammation [6].Endometriosis is also determined by neurovegetativefactors. Pain is a major cause of physical, psycho-social,emotional and professional or work-related impairmentamong women with endometriosis. Recently, severalstudies indicated specific nerve fibres present in endometri-otic tissue with existing parallels between density of smallnerve fibres and pain severity [6–8]. In a double-blindstudy, Fraser et al. employed diagnostic laparoscopy andsubsequent nerve fibre analysis in endometrial biopsies fordiagnostic purposes. They were able to show that nervefibre analysis in endometrial biopsies was nearly as reliablefor diagnosing endometriosis as laparoscopy performed byexperienced gynaecological laparoscopists [8]. Fraser et al.were also able to show that combined oral contraceptivesand progestogens significantly reduced nerve fibre densityand nerve growth factor and cognate receptors in peritonealendometriotic lesions [6].Given the severe clinical symptoms of endometriosis,such as chronic pain and infertility, it is not surprising thatpatients with endometriosis often report poor quality of life,high stress perception and depressive symptoms. Also,patients suffering from endometriosis-related dyspareuniaforbear from informing their (sexual) partners implicating atendency towards a withdrawal and possibly leading tostigmatization and self-pity, further increasing (emotional)stress [9]. Siedentopf et al. [10] reported a reduced qualityof life, increased stress perception and depressive symp-toms in patients with endometriosis, associated with aperitoneal cytokine profile in favour of inflammation.However, analyses of the ex vivo samples did not allowto confirm a positive correlation between psycho-social andinflammatory markers.The wealth of published evidence supporting that (1)endometriosis is associated with a poor quality of life and