Antiestrogenic effect of clomiphene citrate: correlation with serum estradiol concentrations.

The antiestrogenic effect of clomiphene citrate (CC) on cervical mucus was evaluated in women receiving 150 mg CC daily for 5 days. Daily cervical mucus scores and serum estradiol (E2) concentrations were determined in control (n = 25) and CC (n = 24) cycles. E2 concentrations were significantly higher in the CC-treated women (mean +/- standard error of the mean, 1254 +/- 102 pg/ml versus 337 +/- 18 pg/ml, P less than 0.0001). Despite supraphysiologic E2 concentrations, however, cervical mucus scores were significantly reduced in the CC-treated group (P less than 0.01). These data indicate that CC exerts a direct suppressive effect on cervical mucus despite markedly increased E2 concentrations.