The human corpus luteum: life cycle and function in natural cycles

Objective: To summarize recent advances in the understanding of the endocrine signaling pathways between the hypothalamus, pituitary, and human corpus luteum (CL); to examine the major paracrine and autocrine mechanisms and the key genes and proteins involved in CL development, function, and regression in natural cycles; to review the endocrine and molecular response of the midluteal phase CL to in vivo administration of human chorionic gonadotropin (hCG); and to describe the ultrasonographic and Doppler evaluation of the ovary and endometrium throughout the luteal phase. Design: Published data in the literature, including the basic and clinical research studies of the authors. Setting: University-affiliated hospital and research centers. Patient(s): None. Intervention(s): None. Main Outcome Measure(s): Clinical and molecular analysis of human CL function. Result(s): The endocrine function of the subpopulations of luteal cells is critical for the maintenance of CL function, including neovacularization and steroid hormones production. We consider the key genes and proteins that favor development of luteal structure and function throughout the menstrual cycle and in our model of hCG treatment resembling early pregnancy. Conclusion(s): These data indicate that the functional lifespan of the CL depends on paracrine and autocrine mechanisms. Therefore, the significance of the key genes and proteins that we analyze in lutein cells during CL development, function, demise, and rescue by hCG is likely to bring new therapeutic applications for the management of fertility defects and the control of fertility. (Fertil Steril (R) 2009;92:1067-79. (C)2009 by American Society for Reproductive Medicine.)