Acute Effects of Progesterone on LH Pulses During the Follicular Phase (CRM006)

The rapidity with which progesterone slows LH (and by inference GnRH) pulse frequency in women is unclear. The investigators hypothesize that progesterone slows LH pulse frequency within 10 hours. The investigators propose to assess this further with a randomized, cross-over, placebo-controlled study. Regularly cycling women without hyperandrogenism will be admitted to the Clinical Research Unit on cycle day 5-9 (mid-follicular phase) for a 10 hour frequent sampling study to observe LH, FSH, estradiol, progesterone, and testosterone. Either oral micronized progesterone suspension or placebo will be administered at 0900 h. During a subsequent menstrual cycle, subjects will undergo another study identical to the first except that oral progesterone will be exchanged for placebo or vice versa in accordance with a crossover design.