Studies on the mechanism of action of continuous microdose quingestanol acetate.
The contraceptive mechanism of action of quingestanol acetate administered as a minipill was investigated in five healthy, ovulating women. Each woman served as her own control and was studied during a normal menstrual cycle followed by a cycle in which she received quingestanol acetate, 300 mug/day given orally beginning on cycle day 1, for 30 days. Urinary estrone, estradiol, estriol, total estrogens, pregnanediol; serum progesterone, follicle-stimulating hormone, and luteinizing hormone, together with cervical mucus properties (including viscosity, ferning, spinnbarkheit, cell content, pH, and proteins), sperm transport through mucus, vaginal cytology, and basal body temperature were studied serially during the control and study cycles. Endometrial biopsy specimens were obtained at the end of each cycle. The results indicated that all control cycles were ovulatory. In the treated cycles, endometrial morphology was slightly altered. There was also suppression of preovulatory follicle-stimulating hormone and luteinizing hormone peaks, alteration of urinary estrogens, and a decrease in serum progesterone during the luteal phase. Cervical mucus properties and sperm penetration were inhibited to varying degress during the treatment cycle. These findings suggested that at least three different factors, i.e., alteration of ovulation, disturbances of corpus luteum function, and cervical mucus changes causing inhibition of sperm penetration, were involved in the contraceptive mechanism of microdose quingestanol acetate.