A primary focus for endocrine screens has been on the Hypothalamic-Pituitary-Gonadal axis. General screening assays to evaluate a chemical or environmental samples (water or soil) potential for estrogenic or androgenic activities is a first tier approach.
Estrogen (ER) and Androgen (AR) receptor transactivation assays that test for chemical ER or AR agonists are designed to identify estrogenic or androgenic functional activity. This means that if a positive response is measured in the system, the response is due to chemical binding to the ER or AR receptor and subsequent binding of the chemical-receptor complex to the respective DNA response elements (ERE or ARE regions) to induce the expression of a reporter gene, such as luciferase. Chemical antagonism can also be assessed by evaluating the test chemicals ability to activate the signaling pathway in the presence of the endogenous ligand (e.g. estrogen) at a single concentration. A diminished response in luciferase expression when compared to estrogen alone would indicate antagonism