Progesterone is a steroid secreted by the corpus luteum and placenta. It is responsible for preparing the uterine lining for implantation of a fertilized ovum and to maintain pregnancy. Gestodene is a synthetic progesterone analog (i.e., a progestin) that is structurally related to testosterone . A USP-approved grade of gestodene is often formulated in combination with ethynyl estradiol and provided for use as an oral contraceptive. Gestodene offers a pharmacokinetic advantage over the other progestins in that it is directly active (the others are prodrugs), has high bioavailability, and is androgenically neutral. Gestodene does not bind the estrogen receptor (ER); however, two of its A-ring metabolites can bind ER and possess weak estrogenic activity.
