Altrenogest(A35957; RU2267) is a progestogen structurally related to veterinary steroid trenbolone.Target: Progesterone ReceptorAltrenogest is a progestogen structurally related to veterinary steroid trenbolone. Treatment of embryo-recipient mares with altrenogest appears to be beneficial in extending the degree of donor-recipient synchrony required for successful embryo transfer. Altrenogest treatment also seems to be conductive to pregnancy maintenance in recipients experiencing luteal