During early puberty, LH frequency increases during sleep; but in late puberty, LH frequency decreases overnight. Nonetheless, nocturnal LH frequency is similar (~0.5 pulses per hour) in early and late pubertal girls. Preliminary data in early pubertal girls suggests that progesterone acutely slows waking LH frequency, but does not acutely change nocturnal LH frequency. We hypothesize that daytime LH frequency is regulated primarily by sex steroid negative feedback, while sleep-associated LH frequency is not; and that androgens interfere with sex steroid suppression of daytime LH frequency. We propose to assess this further using a protocol in which short-term Progesterone and placebo is given to late pubertal girls (in a cross-over fashion), with subsequent assessment of LH pulse frequency (with sampling occurring while awake and while asleep). We propose that any effect of Progesterone will be blunted or absent in late pubertal girls with hyperandrogenemia.