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.