Study of possible association between endometriosis and phthalate and bisphenol A by biomarkers analysis

Abstract

Endocrine disrupting chemicals (EDCs) such as phthalates and bisphenol A (BPA) are substances that may interfere with the actions of endogenous hormones and may be associated with estrogen-related diseases such as endometriosis. This paper describes a case-control study to evaluate the relationship between endometriosis and phthalates and BPA exposure, through biomarkers analysis in urine. The biomarkers of exposure analyzed were metabolites mono-methyl phthalate, mono-isobutyl phthalate (MiBP), mono-butyl phthalate, mono-cyclohexyl phthalate, mono-(ethylhexyl) phthalate, mono-isononyl phthalate, mono-octyl phthalate (MOP), mono-benzyl phthalate and BPA. Urine samples were collected from women aged 18-45 years old. The Study group (n = 30) and Control group (n = 22) were composed of women using as criteria confirmation of endometriosis by videolaparoscopy surgery with histological diagnosis and the absence of the disease, respectively. The analytical method used liquid phase microextraction with determination by gas chromatography coupled to mass spectrometry. The concentrations of biomarkers were adjusted by the creatinine concentration in urine samples of the two groups. The values obtained for the Study Group were compared with the values obtained for the Control Group. The chi-square test and Odds Ratio were used to compare dichotomized phthalate metabolites and BPA metabolite by endometriosis. All nine metabolites were found in different concentrations in the urine samples in both groups The phthalate metabolites that had the highest concentrations, were MOP and MiBP, in which the values of 670 μg g^-1 and 560 μg g^-1, respectively. The relationship between endometriosis and the all grouped metabolites was evaluated, but was not statistically significant with a 95% CI [X² (df = 1) = 1.471; p = 0.225]. However, odds ratio (95% confidence interval - CI) for MiBP, which was found at relatively high concentrations in the samples, by endometriosis was 1.929 (0.507-7.332). The food habits and gynecologic history were evaluated and no difference was found between groups. Although no evidences of causal link was found, this study contributes to show that other analysis must be done for evaluating the association between endometriosis and compounds suspected of being EDC.

Keywords: Biomarkers; Bisphenol A; Endocrine disrupting chemicals; Endometriosis; Phthalates.