In the further study we have employed the Zebrafish gene expression microarray (v2) as a discovery platform to analysis the trancriptome of 5dpf (days post fertilization) embryos exposed from the 2dpf to 5dpf to nanomolar concrations of thyoid hormone. Only less than 5% genes were affected by the treatment. Gene ontology (GO) analyses show that these genes are involved in the haematopoietic system, visual function and skeletal system. Representatives of each GO functional groups were selected and quantified by real-time PCR to validate the microarray data and to use them as a quantitative biomarkers of thyroid receptor activator. Overall design: The gene expression in Zebrafish was measured in 5 dpfs embryos under 72h Thyroid Hormone treatment at 50nM.