The effect of a synthetic progestogen, ethylnorgestrienone, on hypothalamic-pituitary-ovarian function, cervical...

The antifertility mechanism of a new progestin preparation, ethylnorgestrienone (13 beta-ethyl-17 alpha-ethynyl-17-hydroxy-gona-4,9,11-triene-3-one) (R2323), was evaluated. The compound was administered orally in doses of 5 mg weekly to seven subjects for a total of nine treatment cycles. Each woman served as her own control and was studied during a normal menstrual cycle followed by a cycle in which she received R2323. Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, and progesterone, as well as cervical mucus properties, were studied serially during the control and treatment cycles. Results indicated that all control cycles were ovulatory. Ovulatory gonadotropin patterns were observed in four treated cycles, but preovulatory FSH and LH peaks and progesterone production during the luteal phase were suppressed significantly. Estradiol levels showed an early increase during the follicular phase and a significantly decreased preovulatory peak. Cervical mucus properties were altered and sperm penetration in cervical mucus was inhibited in all treatment cycles. These findings suggest that at least two different factors might be involved in the contraceptive mechanism of R2323: (1) alteration of the ovulatory process and progesterone production, and (2) cervical mucus changes leading to inhibition of sperm migration.