Immune Aspects and Myometrial Actions of Progesterone and CRH in Labor

Figure 2

The role of CRH in human labor. CRH is produced in the placenta in response to stimuli that either increase (oxytocin, PG, stress) or decrease (progesterone) its production. CRH acts on fetal pituitary to increase ACTH production. ACTH and CRH act on fetal adrenals that produce DHEA-S and cortisol. DHEA-S is metabolized in the placenta to estrogens that increase myometrial contractions and facilitate labor. Cortisol acts on fetal lungs which produce SP-A, which also increases uterine contractility. Furthermore, placental CRH acts directly on human myometrial cells via its receptors CRH-R1, -R2, to facilitate the transition from uterine quiescence to myometrial contractions during labor. CRH: corticotrophin-releasing hormone, PG: prostaglandins, ACTH: adrenocorticotropic hormone, DHEA-S: dehydroepiandrosterone sulphate, SP-A: surfactant protein A.