Increased exposure to dioxin-like compounds is associated with endometriosis in a case–control study in women

Although endometriosis is thought to be an environmental disorder initiated by dioxin exposure, this association is controversial. This study was performed to test the hypothesis that endometriosis occurs more often in women exposed to higher concentrations of dioxin-like compounds (DLC) than in those women exposed to lower concentrations. Plasma samples collected prior to laparoscopic surgery from 96 women with endometriosis and 106 control patients with a normal pelvis were measured for DLC concentrations using the dioxin-responsive chemical-activated luciferase expression bioassay. The results showed that concentration (mean ± SD) of DLC was marginally higher in patients with endometriosis (22.3 ± 9.3 pg CALUX-TEQ/g lipid) than in controls (20.5 ± 10.8 pg). After categorization of patients in a group with ‘low’ plasma concentrations (<25th centile) and a group with ‘high’ plasma concentrations (>75th centile) of DLC, the age-adjusted odds ratio to have endometriosis was 2.44 (95% CI 1.04–5.70; P = 0.04) for women with high concentrations of DLC and it increased to 3.01 (95% CI 1.06–9.04; P = 0.03) when only women with moderate severe endometriosis were considered. In conclusion, women exposed to higher plasma concentrations of DLC were at higher risk of having endometriosis than women exposed to lower concentrations of DLC within normal environmental concentrations.