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Susan F Evans,1 Yuen Kwok,1 Ann Solterbeck,2 Carmen Pyragius,3 Mary Louise Hull,4 Mark R Hutchinson,1,5 Paul Rolan1 1Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia; 2Statistical Revelations, Melbourne, Victoria, Australia; 3School of Paediatrics & Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia; 4Robinson Research Institute, School of Pediatrics and Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia; 5ARC Centre of Excellence for Nanoscale Biophotonics, University of Adelaide, Adelaide, South Australia, AustraliaCorrespondence: Susan F EvansAdelaide Medical School, University of Adelaide, PO Box 4025, Norwood South, Adelaide, 5067, South Australia, AustraliaTel +61 418 840 895Fax +61 8 8363 2911Email susan.evans@adelaide.edu.auPurpose: Women bear a disproportionate burden of persistent pain conditions when compared to men. To determine whether the hormonal environment affects the clinical experience of pain, as measured by the days per month of pelvic pain (DPelvicPM), period pain (DPeriodPM), headache (DHeadachePM) or the in vitro EC50 for Interleukin-1β (IL-1β) release following TLR4 stimulation with Lipopolysaccharide from Peripheral Blood Mononuclear Cells (PBMCs). Findings were stratified according to use or non-use of the oral contraceptive pill.Patients and Methods: Fifty-six women aged 16– 35 years, with minimal or severe dysmenorrhea, and use or non-use of the OC, were enrolled. Blood was collected on two occasions in a single menstrual cycle: Days 1– 2 and Days 7– 10. Hormonal analysis for testosterone, dihydrotestosterone, dehydroepiandrosterone, Androstenedione, 3α-Androstanediol, 3β-androstanediol, estradiol, estrone, 17α-hydroxyprogesterone, progesterone, cortisol and sex-hormone binding globulin was undertaken using ultra-sensitive Liquid Chromatography Mass–Spectrometry (LC-MS). PBMCs were exposed to lipopolysaccharide (LPS) and the resulting Interleukin-1β output was determined.Results: Non-users of the OC showed a strongly inverse correlation between a reducing free androgen index (FAI) and increasing DPelvicPM (p=0.0032), DPeriodPM (p=0.013), DHeadachePM (p=0.041). Non-users of the OC showed a significant increase in DPelvicPM (p=0.049) on Days 7– 10. Modestly significant associations were found between reduced androgens and potentiated LPS-induced IL-1β (lower EC50).Conclusion: This is the first study to investigate the relationship between the hormonal environment and activation of the immune system in young women with dysmenorrhoea-related pain conditions. Low androgen levels were consistently associated with increased pain. Translational implications for the findings are discussed.Keywords: pain, testosterone, oral contraceptive pill, dysmenorrhoea, pelvic pain, IL-1β

Susan F Evans,1 Yuen H Kwok,2 Ann Solterbeck,3 Jiajun Liu,2 Mark R Hutchinson,1,4 M Louise Hull,5 Paul E Rolan6 1Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia; 2Faculty of Health Science, University of Adelaide, Adelaide, South Australia, Australia; 3Statistical Revelations, Melbourne, Victoria, Australia; 4Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, University of Adelaide, Adelaide, South Australia, Australia; 5Robinson Research Institute, School or Pediatrics and Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia; 6School of Medicine, University of Adelaide, Adelaide, South Australia, AustraliaCorrespondence: Susan F Evans Tel +61 418 849 895Email susan.evans@adelaide.edu.auPurpose: Dysmenorrhea is a common disorder that substantially disrupts the lives of young women. To determine whether there is evidence of activation of the innate immune system in dysmenorrhea and whether the degree of activation may be used as a biomarker for pain, we compared the responsiveness of peripheral blood mononuclear cells (PBMCs) to toll-like receptor (TLR) 2 or 4 stimulation. We also investigated whether this effect is modulated by the use of the oral contraceptive pill (OC).Patients and Methods: Fifty-six women aged 16– 35 years, with either severe or minimal dysmenorrhea, and use or non-use of the OC, were enrolled. PBMCs were collected on two occasions in a single menstrual cycle: the menstrual phase and the mid-follicular phase. PBMCs were exposed to lipopolysaccharide (LPS), a TLR4 agonist, and PAM3CSK4 (PAM), a TLR2 agonist, and the resulting interleukin-1beta (IL– 1β) output was determined. Statistical analysis compared the EC50 between groups as a measure of TLR responsiveness of PBMCs.Results: The key finding following LPS stimulation was a pain effect of dysmenorrhea (p=0.042) that was independent of use or non-use of OC, and independent of day of testing. Women with dysmenorrhea showed a large 2.15-fold (95% CI − 4.69, − 0.09) increase in IL– 1β release when compared with pain-free participants across both days.Conclusion: This is the first study to demonstrate an ex vivo immune relationship in women with dysmenorrhea-related pelvic pain. It provides evidence for the potential of immune modulation as a novel pharmacological target for future drug development in the management of dysmenorrhea.Keywords: pain, chronic pain, oral contraceptive pill, endometriosis, pelvic pain, IL-1β