Fig. 9. Integrated luteinizing hormone (LH) surge, days −1 to +1. Daily blood samples were obtained in normal women and women with luteal phase deficiency across the menstrual cycle. The peak LH level at mid cycle was identified as the day of the LH surge (day 0). The elevated daily LH levels on either side of day 0, which were part of the LH surge, were combined (integrated) and compared between the two groups. The integrated LH surge levels for women with luteal phase deficiency were significantly lower than normal when LH was assayed in a standard radioimmunoassay and a Leydig cell bioassay.