"Hormone of darkness" and human reproductive process: direct regulatory role of melatonin in human corpus luteum

Corpora lutea were obtained from normally menstruating women (25–38 years old) in the midluteal phase (days 5–6 from ovulation) at the time of surgery for non-endocrine gynecologic diseases. The protocol was approved by the institutional review board of Università Cattolica del Sacro Cuore in Rome and all patients provided written informed consent. The corpora lutea were dated on the basis of the presumptive day of ovulation (day 0) , determined by urinary luteinizing hormone (LH) peak, ultrasound detection of corpus luteum or disappearance of the dominant follicle, and a rise in the plasma P concentration. ELISA or EIA kit and immunohistochemistry were performed.