Segesterone (INNTooltip International Nonproprietary Name, USANTooltip United States Adopted Name),[1][2] also known as 17α-hydroxy-16-methylene-19-norprogesterone or as 17α-deacetylnestorone, is a steroidalprogestin of the 19-norprogesterone group that was never marketed.[3] An acetateester, segesterone acetate, better known as nestorone or elcometrine, is marketed for clinical use.[4] Segesterone acetate produces segesterone as a metabolite.[5]