Progestational effects of dydrogesterone in vitro, in vivo and on the human endometrium.

Dydrogesterone has a molecular structure closely related to that of natural progesterone, but it has enhanced oral availability compared with progesterone. The hormonal profile and the progestational potency of dydrogesterone has been determined in vitro, in vivo and in humans, in combination with estrogens or without. It showed varying affinity for progesterone-binding proteins in uterine tissue in vitro, depending on the species. It exerted a clear progestational response in the rabbit in vivo, although the potency was influenced somewhat by the route of administration. When used in hormone replacement therapy, 10mg dydrogesterone given sequentially provides adequate protection against endometrial hyperplasia in postmenopausal women using 2mg estradiol. Similarly, a dydrogesterone dose of 5mg also protects the endometrium when continuously combined with 1mg estradiol. Dydrogesterone also has beneficial effects in women with amenorrhea/oligomenorrhea, dysfunctional uterine bleeding and irregular cycles. In conclusion, having a similar profile to progesterone but with better oral availability, dydrogesterone has been used successfully to treat disorders related to absolute or relative progesterone deficiency.