 Dydrogesterone binds to and activates both of the major isoforms of the PR, the PR-A and PR-B, with a similar selectivity ratio between the two receptors as that of progesterone and with lower efficacy at the receptors relative to progesterone.The major active metabolite of dydrogesterone, 20α-dihydrodydrogesterone (20α-DHD), has progestogenic activity as well but with greatly decreased potency relative to dydrogesterone.As with other progestogens, dydrogesterone has functional antiestrogenic effects in certain tissues, for instance in the endometrium, and induces endometrial secretory transformation.