The purpose of this study was to test the primary hypothesis that exogenous progesterone, given in the early morning, acutely (within 12 h) suppresses waking LH pulse frequency in estradiol‐pretreated normally cycling women, but to a lesser degree in estradiol‐pretreated women with PCOS (i.e., that acute progesterone negative feedback on waking LH pulse frequency is impaired in PCOS). The gene discussed is PLOD1; the disease is polycystic ovary syndrome.