Relationship between Cyst Fluid Concentrations of Iron and Severity of Dysmenorrhea in Patients with Ovarian Endometrioma

<b><i>Objectives and Design:</i></b> Endometriosis-related pain can be caused by anatomical distortions as well as environmental factors such as inflammation and oxidative stress. The aim of this study is to investigate the relationship between the severity of dysmenorrhea in patients with ovarian endometrioma (OMA) and cyst fluid (CF) concentrations of irons, including total iron, heme iron, and free iron. <b><i>Method:</i></b> Eighty-three patients who were histologically diagnosed with OMA were enrolled in the Department of Gynecology, Nara Medical University Hospital, between 2013 and 2019. The patients were divided into 4 groups according to the severity of dysmenorrhea: no pain, mild, moderate, and severe. Iron concentration was measured by the inductively coupled plasma optical emission spectrometry method. <b><i>Results:</i></b> There were no significant differences among the 4 groups in variables such as age at diagnosis, preoperative CA125, preoperative CA19-9, cyst size, and tumor laterality (unilateral or bilateral). There was a positive correlation between the severity of dysmenorrhea and total iron (<i>p</i> &#x3c; 0.001) and heme iron (<i>p</i> = 0.016) concentrations. Multiple regression analyses revealed that the CF concentration of total iron (hazard ratio 18.75, 95% confidence interval: 2.26–155.35, <i>p</i> = 0.007) was a significant independent variable associated with the severity of dysmenorrhea. A receiver operating characteristic curve analysis showed that a total iron exceeding 290.8 mg/L was associated with severe dysmenorrhea with a sensitivity of 90.9% and a specificity of 65.7%. <b><i>Limitations:</i></b> This study excluded patients with adenomyosis, superficial endometriosis, or deep endometriosis, resulting in a smaller number of cases. Iron levels could not be compared to the endometriosis stage using the r-ASRM score. <b><i>Conclusions:</i></b> There is no clear evidence that iron predicts the severity of endometriosis-related pain. However, iron may be closely associated with dysmenorrhea.