Dydrogesterone is an orally active progestogen which acts directly on the uterus, producing a complete secretory endometrium in an estrogen-primed uterus. At therapeutic levels, dydrogesterone has no contraceptive effect as it does not inhibit or interfere with ovulation or the corpus luteum. Furthermore, dydrogesterone is non-androgenic, non-estrogenic, non-corticoid, non-anabolic and is not excreted as pregnanediol. Dydrogesterone helps to regulate the healthy growth and normal shedding of the uterus lining. Therefore, it may be useful in the treatment of menstrual disorders such as absent, irregular or painful menstrual periods, infertility, premenstrual syndrome and endometriosis. Dydrogesterone works by regulating the healthy growth and normal shedding of the womb lining by acting on progesterone receptors in the uterus. Used to treat irregular duration of cycles and irregular occurrence and duration of periods caused by progesterone deficiency. Also used to prevent natural abortion in patients who have a history of habitual abortions. Dydrogesterone was first introduced to the market in 1961, and is currently approved in over 100 countries world-wide. Banned in the USA and wthdrawn from the UK, but still used in other countries.