In summary, we detected

differences in the estrogenic and/or androgenic activities between categories of ethnic origin (crudely classified as ‘European Caucasian’ vs. ‘other’), age, smoking, alcohol consumption, and prescriptive drug use. The data also indicated associations between several occupational exposures and increased plasma estrogenicity and/or androgenicity, whereas no associations with the intake of specific food items were found. Finally, positive associations were found between internal dioxin levels (TEQs) and androgenic plasma activity. Before interpreting these results, we return to some methodological issues concerning the study design, methods, and analyses that may have influenced our findings. The study

population was recruited among fathers who participated in a case–referent study on hypospadias and cryptorchidism, SCR7 mw so approximately 50% had a son with a urogenital birth defect. Theoretically, a problem could arise if in these fathers, the effects of chemical exposures on plasma hormone activity would substantially differ from other men, but this seems unlikely. However, the fact that all men had Integrase inhibitor fathered children could imply that men with reduced fertility (possibly associated with exposure to endocrine disruptors) were somewhat underrepresented in our population. With the population recruitment strategy, we aimed to obtain a sufficient exposure gradient to identify differences in plasma hormone activities between high and low exposure categories for different sources of potential endocrine disruptors. As a consequence, the reference category of a particular exposure variable may include many subjects that reported other sources of potential endocrine disruptors, which could bias the effect estimate. Although C-X-C chemokine receptor type 7 (CXCR-7) we tried to adjust for confounding by other exposure sources with multivariable analyses, residual confounding cannot be ruled out, especially when the population

size did not allow adjustment for multiple variables simultaneously. This may have led to both underestimated and overestimated effect estimates. The effect estimates may also be affected by exposure misclassification, which most likely resulted in bias towards the null. Overall, the findings of this explorative study should be interpreted with caution and require confirmation by future research. The elevated plasma androgenic activity associated with increased age was unexpected. Increasing age is known to be accompanied by a decline in endogenous free testosterone (Allen et al., 2002, Muller et al., 2003, Svartberg et al., 2003 and Orwoll et al., 2006). Therefore, it seems that our findings result from differences in environmental factors, rather than in endogenous hormone levels, between different ages.