Fig. 10. Progesterone secretion in luteal phase deficiency. Blood samples drawn every 20 minutes for 24 hours in a woman with low integrated progesterone secretion over the duration of her luteal phase (LPD) were assayed for luteinizing hormone (LH) and progesterone (P). The LH changes marked with an asterisk are true secretory pulses, as are the progesterone data points that are circled. The synchrony of LH and progesterone secretion was maintained in women with luteal phase deficiency in the same manner as occurs in normal women.