Authors
Lebel, G., Dodin, S., Ayotte, P., Marcoux, S., Ferron, L,A., Dewailly, E.

Title
Organochlorine Exposure and the risk of Endometriosis

Journal
Fertility and Sterility, 69(2): 221-228 (1998)

Summary
The demonstration that treatment of monkeys with the persistent environmental contaminant TCDD results in an increase in the rate and severity of endometriosis has raised the concern that chemicals in our environment may play a causal role in this disease. Endometriosis is a gynecological disorder that has been estimated to affect between 10 and 15% of women in their reproductive years. It is an estrogen dependent disease characterized by the presence of functional endometrial glands and stroma outside of the uterus. Diagnosis can only be achieved through visual inspection of the pelvis by laparoscopy and histological assessment. The cause of endometriosis remains undetermined although retrograde menstruation is thought to play a key role in the development of the disease. However, retrograde menstruation is a common occurrence in many women and only a fraction develop endometriosis. It is thought that other factors must be contributing to the development of this enigmatic disease. This paper is important because it is the first study that has been specifically designed to investigate the association between exposure to organochlorines and endometriosis. This study makes a unique and valuable contribution to our knowledge base because the author's recruited women who were newly diagnosed with endometriosis compared to women without endometriotic lesions. Specifically, in 1994 women between the ages of 18 and 50 who were undergoing laparoscopy for pelvic pain, infertility or tubal fulguration at a reproductive and endocrinology clinic in Quebec City were selected on a consecutive basis for the study. All laparoscopies were done by gynecologists who were advised to inspect the pelvis according to the standard procedure recommendations by the AFS regardless of the indication for the procedure. In total, there were 86 women with a new diagnosis of endometriosis and 76 women without endometriotic lesions who were matched (1:1) according to their indication for laparoscopy. Blood samples were collected from each woman and later analyzed and lipid adjusted for 14 PCB congeners and 11 chlorinated pesticides. Cases and controls were similar on several confounding factors including age, BMI, history of breastfeeding, use of OCs, smoking habit, mean number of fish meals per week, income and education. More cases than controls had never been pregnant (47% vs 27%) and age and BMI were significantly associated with organochlorine plasma concentrations.

The organochlorine levels in this population were low but similar to those encountered in the general population from industrialized countries. Geometric mean concentrations of ?PCB, ?DDT and ?CHL (the sum of plasma concentration of a-chlordane, ?-chlordane, oxychlordne, cis-nonachlor and trans-nonachlor) were adjusted for age and BMI. The authors found no statistically significant difference between the crude and adjusted geometric mean concentrations of PCBs and chlorinated pesticides when comparing the cases and controls. Multivariate logistic regression using ?PCB, ?DDT and ?CHL as continuous variables, quartiles and tertiles showed no significant or consistent trends in the adjusted odds ratio.

The results of this study suggest that organochlorine concentrations are not associated with endometriosis in the general population. However, due to the fact that the half-life of PCBs is 10 years, measuring organochlorine levels in adulthood may have been a limitation. If exposure to these chemicals during puberty, infancy or in utero plays a key role in the development of endometriosis, this would not have been captured through measurements in adulthood. The authors also suggest that the negative results may be due to the low exposure levels in this population and may not apply to populations with higher doses of organochlorines. The sample size may also have been too small to detect differences. Finally, in light of recent studies from Dr. Rier's laboratory, the compounds selected for analysis in the present study may not be the ones most likely to be associated with this disease.