proestrogen

A substance that acts as an estrogen only after it has been metabolized in the body to an active compound.

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pro·es·tro·gen (')prō-'es-trə-jən or chiefly Brit pro-oes·tro·gen -'ēs- n a precursor of an estrogen that must undergo metabolism before becoming an active hormone

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pro·es·tro·gen (pro-esґtro-jən) a substance that has no estrogenic activity itself but can be metabolized in the body to active estrogen.