Fig. 11. A. Progesterone feedback on the gonadotropin-releasing hormone pulse generator. The graphs on the left and right are 24-hour secretory patterns of luteinizing hormone (LH) in a normal woman. Samples were obtained in the mid follicular phase of two corrective cycles. The graph on the left depicts a relatively rapid LH pulse pattern with an even, relatively low pulse amplitude. The LH secretory pattern on the right occurred in the same woman in a subsequent cycle after she had received 7 days of exogenous progesterone. The exogenous progesterone converted her LH secretory pattern to a pattern that was indistinguishable from the normal luteal phase pattern (lower pulse frequency and higher pulse amplitude). B. Progesterone feedback on the gonadotropin-releasing hormone pulse generator. The graphs on the left and right are 24-hour secretory patterns of LH in a normal woman. Samples were obtained in the mid follicular phase of two corrective cycles. The graph on the left depicts a relatively rapid LH pulse pattern with an even, relatively low pulse amplitude. The LH secretory pattern on the right occurred in the same woman in a subsequent cycle after she had received 7 days of exogenous progesterone. The exogenous progesterone converted her LH secretory pattern to a pattern that was indistinguishable from the normal luteal phase pattern (lower pulse frequency and higher pulse amplitude).