Effects of clomiphene citrate on ovarian function in hypophysectomized rats

On Days 28-30 of age, hypophysectomized rats were treated with oestradiol-17 beta (0.1 mg/day) and/or clomiphene citrate (0.1 mg/day). Subsequent treatment with PMSG (10 i.u., on Day 31) and hCG (10 i.u., on Day 33) was identical for all animals. Rats were killed on Day 34. Treatment with oestradiol-17 beta alone resulted in ovulations of 45.1 +/- 5.5 oocytes/rat (mean +/- s.e.m.). There were no ovulations among animals treated with clomiphene citrate alone but treatment with oestradiol-17 beta and clomiphene citrate resulted in a significant (P less than 0.05) reduction (23.1 +/- 7.6 oocytes/rat) in ovulatory response. Similarly, ovarian weights and serum progesterone concentrations were highest in the oestradiol-17 beta-treated rats, intermediate in those given oestradiol plus clomiphene citrate and the lowest in rats receiving clomiphene citrate alone. We suggest that clomiphene citrate exerts direct ovarian antiovulatory and oestrogen-antagonist actions.