<p>Dienogest acts as an agonist at the progesterone receptor (PR) with weak affinity that is comparable to that of progesterone but has a very potent progestagenic effect in the endometrium, causing endometrial atrophy after prolonged use. It promotes antiproliferative, immunologic and antiangiogenic effects on endometrial tissue. Dienogest reduces the level of endogenous production of oestradiol and thereby suppressing the trophic effects of oestradiol on both the eutopic and ectopic endometrium. Continous administration of dienogest results in hyperprogestogenic and moderately hypoestrogenic endocrine environment, which causes initial decidualization of endometrial tissue. It is an antagonist at androgen receptors, improve androgenic symptoms such as acne and hirsutism [A16570].</p>