 The activity of endogenous ligands (such as the hormones estradiol and testosterone) when bound to their cognate nuclear receptors is normally to upregulate gene expression.This stimulation of gene expression by the ligand is referred to as an agonist response.The agonistic effects of endogenous hormones can also be mimicked by certain synthetic ligands, for example, the glucocorticoid receptor anti-inflammatory drug dexamethasone.