Environmental exposure to dioxins and polychlorinated biphenyls reduce levels of gonadal hormones in newborns: Results from the Duisburg cohort study

Background Endocrine dysfunction related to the hypothalamic–pituitary–thyroid (HPT) and/or the hypothalamic–pituitary–gonadal axis (HPG) is being discussed as underlying developmental adversity of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). This study was done to evaluate effects related to the HPG axis. Methods A birth-cohort study was initiated in the year 2000. Healthy mother–infant pairs were recruited in the industrialized city of Duisburg, Germany. Dioxins, dioxin-like PCBs and six indicator PCBs were measured in maternal blood during pregnancy and in maternal milk. Testosterone and estradiol levels were measured in maternal and cord serum of 104 mother–infant pairs representing a subsample with a complete data set of the total basic sample of 232 participants. Linear regression analysis was used to describe the association of PCDD/Fs or PCB in maternal blood or milk with sex steroid concentrations after adjustment for confounding. Results Median concentrations for PCDD/Fs in maternal blood fat and milk fat in terms of WHO-TEq were 15.3 and 13.1 pg WHO-TEq/g, respectively, and for the sum of the indicator PCBs (#28, #52, #101, #138, #153, #180) 149 and 177 ng/g. The adjusted ratio of geometric means when doubling the concentration of PCDD/Fs in maternal blood fat was 0.86, 95% confidence interval (95% CI): 0.72–1.03 for testosterone and 0.73 (0.61–0.87) for estradiol in cord serum. Typically, testosterone reduction was more pronounced in cord serum of female and estradiol reduction in that of male babies. Reduction of hormone levels was generally more pronounced for dioxins than for indicator PCBs. Conclusions The hypothalamic–pituitary–gonadal axis of newborn babies is influenced by prenatal exposure to PCDD/Fs and PCBs in a manner suggestive of AhR-mediation. The clinical relevance of this finding remains to be established, however.