{"paper_id":"9860074a-916c-4c67-84af-57c134b6fdfc","body_text":"Abstract\nObjective\nTo evaluate the association between serum 25-hydroxyvitamin D [25(OH)D] levels and pain severity in women with surgically and histopathologically confirmed endometriosis, and to assess whether this association differs between ovarian endometrioma (OE) and deep infiltrating endometriosis (DIE) phenotypes.\nMethods\nThis retrospective observational analytical study included 427 women with surgically confirmed endometriosis. Patients were classified according to dominant phenotype as OE (n=231) or DIE (n=196). Serum 25(OH)D levels were categorized as deficient (<20 ng/mL), insufficient (20–30 ng/mL), and sufficient (≥30 ng/mL). Pain severity—including dysmenorrhea, chronic pelvic pain, and dyspareunia—was assessed using the Visual Analog Scale (VAS). Multivariable linear regression analyses were performed to examine the association between vitamin D levels and pain scores, adjusting for age, body mass index, and seasonal variation.\nResults\nSerum 25(OH)D levels were inversely associated with all pain parameters (p<0.001). Patients with vitamin D deficiency had higher median VAS scores compared to those with sufficient levels [7.0 (6.0–8.0) vs 4.0 (3.0–5.0), p<0.001]. In multivariable analyses, lower 25(OH)D levels remained significantly associated with higher pain severity (β = -0.28, p<0.001). A significant interaction between vitamin D levels and disease phenotype was observed (interaction p=0.004), suggesting that the association between lower vitamin D levels and higher pain scores was more pronounced in patients with the DIE phenotype compared to those with OE. A threshold value of 18.5 ng/mL demonstrated 74% sensitivity for identifying patients with severe pain (VAS ≥7).\nConclusion\nLower serum vitamin D levels are significantly associated with greater pain severity in women with endometriosis, with a stronger association observed in the DIE phenotype. However, given the retrospective and cross-sectional nature of the analysis, causality cannot be inferred. Prospective studies are needed to further clarify these associations and their potential clinical implications.\nSimilar content being viewed by others\nAbbreviations\n- 25(OH)D:\n-\n25-hydroxyvitamin D\n- AUC:\n-\nArea under the curve\n- BMI:\n-\nBody mass index\n- CA125:\n-\nCancer antigen 125\n- CI:\n-\nConfidence interval\n- CPP:\n-\nChronic pelvic pain\n- DIE:\n-\nDeep infiltrating endometriosis\n- GnRH:\n-\nGonadotropin-releasing hormone\n- IQR:\n-\nInterquartile range\n- NRS:\n-\nNumeric Rating Scale\n- OE:\n-\nOvarian endometrioma\n- PPV:\n-\nPositive predictive value\n- NPV:\n-\nNegative predictive value\n- rASRM:\n-\nRevised American Society for Reproductive Medicine\n- ROC:\n-\nReceiver operating characteristic\n- SPSS:\n-\nStatistical Package for the Social Sciences\n- VAS:\n-\nVisual Analog Scale\n- VDBP:\n-\nVitamin D binding protein\n- VDR:\n-\nVitamin D receptor\nAcknowledgements\nNot applicable.\nFunding\nThe authors received no financial support for the research, authorship, and/or publication of this article.\nAuthor information\nAuthors and Affiliations\nCorresponding author\nEthics declarations\nEthics approval and consent to participate\nThis retrospective observational study was approved by the Ethics Committee of University of Health Sciences Turkey, Kartal Dr. Lütfi Kırdar City Hospital (Approval No: 2026/010.99/25/7, Date: 24.02.2026. Due to the retrospective design of the study and the use of anonymized patient data, the requirement for informed consent was waived by the ethics committee. The study was conducted in accordance with the Declaration of Helsinki.\nConsent for publication\nNot applicable.\nCompeting interests\nThe authors declare no competing interests.\nAdditional information\nPublisher’s Note\nSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\nRights and permissions\nOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.\nAbout this article\nCite this article\nBaglar, I., Sanlikan, F., Keles, E. et al. Vitamin D deficiency and pain severity in endometriosis: a phenotype-based retrospective observational study. BMC Women's Health (2026). https://doi.org/10.1186/s12905-026-04542-8\nReceived:\nAccepted:\nPublished:\nDOI: https://doi.org/10.1186/s12905-026-04542-8","source_license":"CC0","license_restricted":false}