The luteinizing hormone surge: timing and characteristics in the plasma and urine after clomiphene citrate treatment.

Clomiphene citrate (CC) has been used to influence the timing of ovulation. To evaluate the effects of CC on the timing of the luteinizing hormone (LH) surge, we examined the LH surge in 10 cycling normal women for 3 cycles each, during an untreated cycle (control) and during treatment with 50 mg CC (CC 50) and 150 mg CC (CC 150) daily on days 5 to 9. Length of control cycles (mean +/- standard error of the mean) was 28.5 +/- 1.1 days and was not significantly different from either CC 50 (28.2 +/- 0.6 days) or CC 150 cycles (29.0 +/- 0.4 days). LH surge occurred on day 16.4 +/- 1.2 in control, 16.5 +/- 0.5 in CC 50, and 17.1 +/- 0.7 in CC 150 cycles. Similarly, luteal phase lengths were not significantly affected by CC treatment. Individually, however, the effect of CC on the timing of the LH surge depended on when the LH surge occurred in corresponding control cycles. If the control cycle LH surge occurred on day 16 or earlier, CC significantly delayed it. If the normal LH surge occurred on day 18 or later, CC advanced it. During CC 50 treatment, the LH surge was advanced by 1 to 7 days in 3 cycles, unchanged in 2, and delayed in 5 cycles by 1 to 9 days. Detection of urinary LH surge was reliable in CC-treated cycles and correlated well with the day of plasma LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)