For the evaluation of effects of hormone-active substances to fish, several test guidelines have been validated by the OECD which are included in the Conceptual Framework for Testing and Assessment of Endocrine Disruptors (OECD, 2010). In these tests, the assessment of physiological parameters is limited to the established biomarkers like vitellogenin or 11-keto testosterone in blood plasma or liver tissue. A promising approach
to refine existing testing strategies is the integration of molecular endpoints, which rapidly respond to exposure. Furthermore, these endpoints can be indicative of potential adverse effects at the organismal level by providing information, which connect to the initiating effect of a substance. This is in line with the concept of Adverse Outcome Pathways (AOP), which evolved from the “toxicity pathway” approach as a mechanistic evaluation tool for the risk assessment.