Obstetrics and Gynecology · 2002 · 208 citations · 28 references
MedicineGynecologyPharmacologyContraceptionReproductive EndocrinologyReproductive MedicineContraception PharmacotherapyContraceptive PharmacotherapyEmergency ContraceptionFemale ContraceptionHormonal ContraceptionOvarian PhysiologyCytokines In Endometrial ReceptivityEndometrial MaturationEndometrial ProliferationEstrogen-progestin ContraceptionLevonorgestrel Emergency ContraceptionOvarian Function AssessmentOvarian Function TestingProgesterone Receptors
The study aimed to evaluate how mifepristone and levonorgestrel affect ovarian function and endometrial development at emergency contraception doses. The authors assessed endometrial maturation and receptivity markers (integrins, COX enzymes, progesterone receptors, lectin binding, pinopodes) via biopsy, and measured urinary LH, estrone, and pregnanediol levels before and after treatment. Both drugs mainly prevented ovulation, as evidenced by suppressed LH surge and unchanged endometrial receptivity markers, indicating that emergency contraception acts by inhibiting ovulation rather than implantation.
To study the effect of mifepristone and levonorgestrel on ovarian function and endometrial development in doses effective as emergency contraception.Twelve fertile women were treated with either 10 mg of mifepristone as a single dose (n = 6) or two doses of 0.75 mg of levonorgestrel, 12 hours apart (n = 6) before and after ovulation. An endometrial biopsy performed during the implantation period was analyzed for endometrial maturation and expression of markers of endometrial receptivity. The markers tested for were integrin alpha4 and beta3, cyclooxygenase-1 and -2, progesterone receptors, Dolichos biflorus agglutinin lectin binding, and pinopodes. Urinary excretion of luteinizing hormone, estrone, and pregnanediol were also determined.Treatment with mifepristone and levonorgestrel before ovulation inhibited the luteinizing hormone surge showing no significant differences between the means of luteinizing hormone measurements. When mifepristone was administered in the early luteal phase, downregulation of progesterone receptors was inhibited in five of six women. No significant alteration was found in any of the remaining markers of endometrial receptivity.The mode of action of emergency contraception with mifepristone or levonorgestrel is primarily due to inhibition of ovulation rather than inhibition of implantation.
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