Environmental exposure to metals and male reproductive hormones: circulating testosterone is inversely associated with blood molybdenum

Objective To explore associations between exposure to metals and male reproductive hormone levels. Design Cross-sectional epidemiology study with adjustment for potential confounders. Setting University Medical Center. Patient(s) Men recruited through two infertility clinics in Michigan. Intervention(s) Metal concentrations and reproductive hormone levels were measured in blood samples collected from 219 men. Main Outcome Measure(s) Serum FSH, LH, inhibin B, T, and sex hormone-binding globulin levels. Result(s) Cadmium, copper, and lead were all significantly or suggestively positively associated with T when modeled individually, findings that are consistent with limited previous human and animal studies. Conversely, molybdenum was associated with reduced T. A significant inverse trend between molybdenum and T remained when additionally considering other metals in the model, and a positive association between T and zinc was also found. Finally, in exploratory analysis there was evidence for an interaction between molybdenum and zinc, whereby high molybdenum was associated with a 37% reduction in T (relative to the population median level) among men with low zinc. Conclusion(s) Although reductions in T and reproductive toxicity after molybdenum exposure have been previously demonstrated in animal studies, more research is needed to determine whether molybdenum poses a risk to human reproductive health.