Corpus luteum rescue in nonhuman primates and women

The primate corpus luteum undergoes a process at the end of a nonfertile menstrual cycle termed luteolysis, which involves considerable structural and functional changes that lead to a loss in the ability to produce the steroid hormone progesterone. Because progesterone is critical for events involved in embryo implantation and sustaining pregnancy, the survival and continued function of the corpus luteum are required throughout the fi rst weeks of pregnancy, after which the placenta becomes responsible for the maintenance of gestation. Extension of the functional lifespan of the primate corpus luteum is achieved through the secretion of chorionic gonadotropin (CG) from the conceptus. CG signals through the luteinizing hormone-chorionic gonadotropin receptor (LHCGR) located on luteal cells to override the cellular and molecular events that are responsible for the demise of the corpus luteum during nonfertile cycles. Thus, in this chapter, the source of various CG forms and the regulation of their production, as well as the mechanisms through which LHCGR signaling regulates cellular activities in the primate corpus luteum during early pregnancy are reviewed. Also, current and possible uses of hCG forms for diagnosis and treatment of infertility and pregnancy disorders are considered.