Active Immunization to 17β-Estradiol and Its Effects upon the Reproductive Cycle of the Rhesus Monkey

Fourteen rhesus monkeys were immunized to estradiol-17-hemisuccinyl-BSA. All 11 monkeys immunized with doses of 1.5 to 3.0 mg of the antigen developed antibodies to estradiol. In 7 of these animals, the antibody titers remained above 30& binding for the duration of the immunization. No titers were detected in 3 animals immunized with 4 to 6 mg of the antigen. Monkeys with persistently high antibody titers became anovulatory, as determined by low progestin levels and the absence of corpora lutea. The vaginal smears lost cyclicity and the intervals between uterine bleedings became irregular and lengthened. Average basal LH levels increasedsignificantly above controls but remained below those of castrated animals. Vaginal smears and uterine histology indicated a persistent estrogen stimulation. After a prolonged period of immunization, the ovaries were enlarged and multiple cystic follicles were present. Diethylstilbestrol, at doses of ISO to 750 μg in oil, induced a LH surge in 12 out of 18 experiments performed in monkeys with high antibody titers. In seven instances, this LH surge was followed by ovulation, as indicated by increased blood progestin levels. These results confirm previous experimental evidence for a causal relationship between the midcycle rise in estrogens and LH release in the primate (Endocrinology94: 765, 1974)