Dydrogesterone is characterised by progestational and PR-mediated antiestrogenic activity.  This is demonstrated by its ability to induce a secretory transformation in the endometrium of immature or ovariectomised animals after they have been primed with estrogens (cf. the Clauberg test ). The oral progestogenic potency of dydrogesterone is 20 times higher than that of progesterone.  The progestational efficacy and potency of dydrogesterone was confirmed by standard test (. delay of menses and induction of withdrawal bleeding). The benefits of estrogen or other target organs are not compromised by dydrogesterone.