Paroxypropione (brand names Frenantol, Frenormon, Hypophenon, Paroxon, Possipione, Profenone is a synthetic, non-steroidal estrogen that has been used medically as an antigonadotropin in Spain and Italy. Paroxypropione was first synthesized in 1902. Its antigonadotropic properties were discovered in 1951 and it entered clinical use shortly thereafter. Paroxypropione is a product from the oxidative splitting of stilbestrol, with a low degree of estrogenicity, has been found a valuable drug for checking the growth of lung metastases secondary to certain malignant tumors such as chorionepitheliomas or nephrobiastomas. As the drug possesses relatively low affinity for the estrogen receptor and must be given at high dosages to achieve significant estrogenic and antigonadotropic action.