Effects of postovulatory estradiol benzoate administration on women's ovarian function

The effects of postovulatory estradiol benzoate (EB) administration were studied in six women having normal biphasic, presumably ovulatory, menstrual cycles. EB was administered intramuscularly at dose levels of 0.5 and 10 mg daily for 5 consecutive days. The study covered a total of 30 cycles; parameters studied were basal body temperature, urinary excretion of estrogens and pregnanediol, and characteristics of cervical mucus. EB had no effect on the length of the luteal phase nor on urinary pregnanediol excretion, but a dose of 10 mg/day caused a significant prolongation of the next follicular phase. The elevated estrogen excretion observed at the end of the cycle supports the hypothesis that gestagenic deprivation causes menstrual bleeding.