BLOCKAGE OF THE POSITIVE FEEDBACK EFFECT OF OESTRADIOL DURING PROLONGED ADMINISTRATION OF CLOMIPHENE CITRATE TO NORMAL WOMEN

The effect of clomiphene citrate on the occurrence and timing of the endogenous LH surge in superovulated cycles is unclear. To study further this event, five normally ovulating women were treated with clomiphene citrate 100 mg per day in two different cycles, that is, for 5 days in one cycle (days 2 to 6, CC-5) and for 15 days in another cycle (days 2 to 16, CC-15). During the CC-5 cycle, the normal pattern of LH levels seen in spontaneous cycles was observed with an endogenous LH surge in all women followed by ovulation and normal luteal function. In contrast, during the CC-15 cycle, a continuous and progressive increase of basal LH levels was seen with no surge, resulting in follicular luteinization but no ovulation. The results suggest that in normal women treated with clomiphene the occurrence of an endogenous LH surge is dependent on a significant decrease in the circulatory concentration of clomiphene at mid-cycle.