The Relationship between Serum Levels of Oxidative Stress Biomarkers and Dysmenorrhea, Dyspareunia and Pelvic Pain in Women with Endometriosis

 Endometriosis is a common disorder associated with an increased risk of cancers, especially ovarian cancer. One of the most prevalent symptoms of this disease is pelvic pain, which is the major complaint among patients during menstruation. While the pathophysiology of endometriosis and the mechanisms responsible for its complications, namely pelvic pain and infertility, are not yet well understood, it seems that oxidative stress plays an undeniable role in the pathogenesis of endometriosis. In other words, the production of large amounts of inflammatory mediators by endometriosis tissue can explain and be responsible for the onset and exacerbation of pelvic pain. There is an apparent imbalance between oxygen free radicals and antioxidants in the endometrial tissue of diagnosed women. In addition, decreased total antioxidant capacity is observed in the peritoneal fluid in women with endometriosis, which is indicative of inadequate antioxidant status. Even though a significant relationship has been reported between symptoms of pelvic pain and indicators of peritoneal oxidative stress in women with endometriosis in some studies, there are still conflicting theories about the relationship between serum biomarkers of oxidative stress and endometriosis. With this background in mind, the present study aimed to determine the relationship between serum levels of oxidative stress biomarkers and dysmenorrhea, dyspareunia, and pelvic pain in women with endometriosis who referred to Sarem Fertility & Infertility Research Center in Tehran, Iran in 2017. 

 This was a descriptive, correlational and cross-sectional study performed on 60 women aged 15-49 years with symptoms of endometriosis. The inclusion criteria were diagnosis of endometriosis based on clinical symptoms and laparoscopy, no current pelvic inflammation disease and adenomyosis, no smoking, or alcohol and drug consumption, no chronic underlying diseases, and no psychological diseases (data were obtained through self-report). Subjects were selected by convenience sampling, and written informed consent was obtained from the participants prior to the study. Data were collected using a demographic characteristics questionnaire, fertility profile questionnaire, endometriosis symptoms checklist, research laboratory information record sheet, and visual analogue scale (VAS) for measuring pain. Following filling out the scales and questionnaires, 10 ccs of the blood sample were taken from each of the volunteers under sterile conditions in citrate tubes and stored after centrifugation at -20°C. Afterwards, blood samples were analyzed, and data analysis was carried out in SPSS version 16 using Pearson’s correlation coefficient. In addition, a P-value of below 0.05 was considered statistically significant. 

 The mean age of the participants was 33.16 ± 5.41 years and the mean age of their spouses was 35.96 ± 8.62. Moreover, the subjects had a body mass index (BMI) of 25.92 ± 5.94 kg/m2, and most of them were housewives (68.3%) and had an academic degree (51.7%). Based on VAS score range of 0-100, the mean score of dysmenorrhea in the subjects was reported to be 50.76 ± 32.90, whereas their mean scores of dyspareunia and pelvic pain were 23.70 ± 25.20 and 21.05 ± 23.49, respectively. Furthermore, most of the participants in the study had no history of previous delivery (83.3%) and abortion (75%). Moreover, dysmenorrhea (96.7%), dyspareunia (66.6%) and chronic pelvic pain (73.3%) were reported in most participants. The results of this study showed that women participating in this study had ROS values of 5.77 ± 0.57 micromoles, TAC of 0.35 ± 0.12 micromoles and MDA of 38.06 ± 24.9 micromoles. According to the results, there was a significant relationship between the level of pelvic pain, dysmenorrhea and dyspareunia.

 In this study, the majority of the participants suffered from pelvic pain, dysmenorrhea and dyspareunia, which was not unexpected due to the fact that endometriosis is the main factor for these conditions. The high prevalence of these pains has been reported in other studies as well. There is a theory that very small recurrent bleeding in endometriosis lesions and subsequent inflammation may be responsible for menstrual cramps. On the other hand, stretching of the uterosacral ligament, which contains endometriosis tissue, during intercourse, as well as the proximity of nerve fibers to abnormal endometrial tissue, may explain the dyspareunia created in these women. Immune system dysfunction due to endometriosis lesions can be another cause of pelvic pain (e.g., endometriosis), which ultimately leads to neuropathic pains. These patients have also reported pelvic pain caused by tissue degradation induced by immune processes. According to the results, there was no relationship between the severity of dysmenorrhea, dyspareunia, and chronic pelvic pain with the number of reactive oxygen species and the total antioxidant capacity of malondialdehyde in the participants. In a research, Amreen et al. mentioned a significant association between glutathione peroxide levels and dysmenorrhea in women with endometriosis. However, oxidative stress was only slightly exacerbated in the subjects. Moreover, the decrease of antioxidants was insignificant in women with endometriosis and chronic pelvic pain, and even the increase in the concentration of lipid peroxides, which occurs in peritoneal fluid, is not observed in the blood. The results were indicative of no significant relationship between chronic leg pain and dyspareunia with levels of oxidative stress biomarkers. It is generally believed that an increase in oxidative stress of those with dysmenorrhea depends on oxygen-free radicals. However, no studies have clearly mentioned the existence and relationship of oxygen-free radical balance and antioxidant systems with dysmenorrhea. Nonetheless, further studies are required to investigate this issue. It is recommended that oxidative stress biomarkers in peritoneal fluid in women with endometriosis be evaluated in future studies.