Corticotropin-releasing hormone, stress and human reproduction: an update

The stress system has suppressive effects on female and male reproductive function. Corticotrophin-releasing hormone (CRH), the principal regulator of stress, has been identified in the female and male reproductive system. Reproductive CRH participates in various reproductive functions that have an inflammatory component, where it serves as an autocrine and paracrine modulator. These include ovarian and endometrial CRH, which may participate in the regulation of steroidogenesis and the inflammatory processes of the ovary (ovulation and luteolysis) and the endometrium (decidualization and blastocyst implantation) and placental CRH, which is secreted mostly during the latter half of pregnancy and is responsible for the onset of labor. It has been suggested that there is a "CRH placental clock" which determines the length of gestation and the timing of parturition and delivery. The potential use of CRH-antagonists is presently under intense investigation. CRH-R1 antagonists have been used in animal studies to elucidate the role of CRH in blastocyst implantation and invasion, early fetal immunotolerance and premature labor. The present review article focuses on the potential roles of CRH on the physiology and pathophysiology of reproduction and highlights its participation in crucial steps of pregnancy, such as implantation, fetal immune tolerance, parturition and fetal programming of the hypothalamic-pituitary-adrenal (HPA) axis.