Interdisciplinary strategies to assess the relationship between exposure to complex chemical mixtures and thyroid hormone system disruption

The possible risk that exposure to chemicals leads to disruption of the thyroid hormone (TH) system in humans and animals can be assessed through biomonitoring of chemicals for which TH system disruption has been demonstrated in animal studies. In addition, epidemiological studies may establish a relationship between exposure to chemicals and adverse outcomes on the thyroid hormone system. However, such studies are often limited to single chemicals or classes of chemicals, and do not account for the complex mixtures to which humans and animals are exposed, consisting of multiple chemicals that in combination may affect similar or different endpoints in the TH system. The use of in vivo, and in vitro studies using complex extracts coming from real-life samples is necessary to unravel the specific effects that chemical mixtures inflict on the TH system. In addition, approaches such as effect-directed analysis that combine bioassays with integrated chemical analysis allow the identification of mixture risk drivers avoiding the loss of chemicals due to excessive sample processing.