To Örebro University

STUDY QUESTION: Are the levels of biologically active and the most toxic dioxin-like substances in adipose tissue of patients with deep infiltrating endometriosis (DIE) higher than in a control group without endometriosis?

SUMMARY ANSWER: DIE patients have higher levels of dioxins and polychlorinated biphenyls (PCBs) in adipose tissue compared with controls without endometriosis.

WHAT IS KNOWN ALREADY: Some studies have investigated the levels of dioxin-like substances, in serum samples, in patients with endometriosis, with inconsistent results.

STUDY DESIGN, SIZE, DURATION: Case-control study including two groups of patients. The study group (DIE group) consisted of 30 patients undergoing laparoscopic surgery because of DIE. In all patients, an extensive preoperative work-up was performed including clinical exploration, magnetic resonance imaging (MRI) and transvaginal sonography. All patients with DIE underwent a confirmatory histological study for DIE after surgery. The non-endometriosis control group (control group), included the next consecutive patient undergoing laparoscopic surgery in our center due to adnexal benign gynecological disease (ovarian or tubal procedures other than endometriosis) after each DIE patient, and who did not present any type of endometriosis.

PARTICIPANTS/MATERIALS, SETTING, METHODS: During the surgical procedure 1-2 g of adipose tissue from the omentum were obtained. Dioxin-like substances were analyzed in adipose tissue in DIE patients and controls without endometriosis.

MAIN RESULTS AND THE ROLE OF CHANCE: The total toxic equivalence and concentrations of both dioxins and PCBs were significantly higher in patients with DIE in comparison with the control group (P < 0.05), mainly due to the significantly higher values of the two most toxic dioxins (2,3,7,8-tetrachlorodibenzo-p-dioxin [2,3,7,8-TCDD] and 1,2,3,7,8-pentachlorodibenzo-p-dioxin [1,2,3,7,8-PeCDD]) (P < 0.01 for each compound). The levels of furan 2,3,4,7,8-PeCDF were statistically higher in the DIE group compared with controls. Only four congeners of PCBs had toxic equivalence values and concentrations that were statistically higher in patients with DIE, but these included the most toxic and carcinogenic PCB-126 (PCB-114 P < 0.05; PCB-156 P < 0.05; PCB-189 P = 0.04; PCB-126 P < 0.01).

LIMITATIONS, REASONS FOR CAUTION: Since fewpatients were recruited, the study is only exploratory. Our results need to be confirmed in larger and more heterogeneous population studies since environmental and even genetic factors involved in determining dioxins and PCBs widely vary in different countries. Furthermore, the strict eligibility criteria used may preclude generalization of the results to other populations and the surgery-based sampling frame may induce a selection bias. Finally, adipose tissue was obtained only from the omentum, and not from other adipose tissue of the body.

WIDER IMPLICATIONS OF THE FINDINGS: Our results suggest a potential role of dioxin-like substances in the pathogenesis of DIE. Further studies are warranted to confirm our findings.