The effects of postnatal exposure of endocrine disruptors on testicular function: a systematic review and a meta-analysis

Background Despite many epidemiological studies having been conducted, the impact of postnatal exposure of endocrine disruptors (EDs) on testicular function remains a controversial issue. Aim To systematically review the literature and perform a quantitative synthesis to evaluate the effect of EDs on testicular function. Materials and methods A comprehensive search was conducted in the MEDLINE, Scopus, and CENTRAL databases. Eligible for the systematic review were observational (cross-sectional and cohort) studies with (i) adult men who had a high probability of postnatal exposure to EDs ("exposed"), (ii) adult men who had a low probability of postnatal exposure to EDs ("non-exposed"), and (iii) an outcome of interest [seminal parameters and reproductive hormone concentrations]. The continuous outcomes in each of the studies were synthesized by the random effects model and expressed as standardized mean difference (SMD) with 95% confidence interval (CI). Results Thirteen studies, including 959 exposed and 907 non-exposed men, fulfilled the inclusion criteria. Exposure to EDs was associated with decreased LH [SMD - 0.17, 95% CI - 0.33 to - 0.02, 10 studies (616 exposed, 563 non-exposed), I-2 40%, p = 0.09], progressive motility [SMD - 0.45, 95% CI - 0.77 to - 0.13, three studies (133 cases, 153 controls), I-2 38%, p = 0.20], and normal morphology [SMD - 0.50, 95% CI - 0.85 to - 0.14, eight studies (562 cases, 540 controls), I-2 87%, p < 0.01] compared with non-exposure. No difference was observed between the other study groups. Conclusions Postnatal exposure to EDs is associated with decreased semen quality. Nevertheless, there is no evidence that a disruption of testicular function mediates the deterioration in semen quality.