Partial agonist

A molecule that binds to a receptor and activates it, but only partially compared to a full agonist. In the context of phytoestrogens, a partial agonist of oestrogen receptors produces a moderate oestrogenic effect, lower than that of endogenous 17beta-oestradiol. During periods of hormonal deficiency such as menopause, this partial effect can be beneficial. During periods of oestrogen excess, the same compound may partially block the action of more potent endogenous oestrogens by occupying receptors without fully activating them, acting as a relative antagonist.