Gonadotropin and Sex Steroid Levels Across the Luteal Phase LH Plasma

A bstract. The pattern of episodic gonadotropin release was studied in 15 normal female volunteers during the luteal phase ofthe menstrual cycle with 24 h ofblood sampling for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels at 10-min intervals. Six subjects (two in the early, two in the mid-, and two in the late luteal phase) also had each of these specimens processed for progesterone levels. A progressive slowing of LH pulsations was present across the luteal phase with the mean LH pulse frequency declining from 15.2 pulses/24 h in the early to 8.4/24 h in the late luteal phase. A trend towards reduction in the amplitude ofLH pulses was also observed (12.3±2.2 SD mIU/ml in the early vs. 8.6±3.4 mIU/ml in the late luteal phase; NS). In addition, LH pulses of heterogeneous amplitude were identified during the same 24-h study. The mean±SD of the larger and of the smaller LH pulses was 16.9±4.7 and 2.3± 1.0 mIU/ml, respectively (P < 0.001). While the slowing of the frequency of all LH pulses correlated well (r = 0.80, P < 0.001) with the day of the luteal phase and poorly with the actual plasma progesterone levels, the incidence of the small LH pulses was highest in the mid-luteal phase and correlated well with the mean progesterone plasma levels (r = 0.63, P < 0.01). In the early luteal phase, the pattern of progesterone secretion was stable over the 24-h studies and showed no