REGULATION OF THE HYPOTHALAMO-PITUITARY-ADRENOCORTICAL AXIS IN FETAL SHEEP

Development of the fetal hypothalamo-pituitary-adrenal (HPA) axis is r equired for normal fetal life and subsequent neonatal health. Activati on of the fetal pituitary gland results in the synthesis and release o f glucocorticoids from the adrenal cortex. Glucocorticoids promote mat uration of several organ systems, are important in responses of the fe tus to stress, and are involved in the initiation of parturition in se veral species. The expression of hypothalamic and pituitary genes asso ciated with HPA function is apparent early in gestation in fetal sheep , although the endocrine changes associated with maturation and partur ition do not occur until the last fifth of gestation. In this connecti on, the fetal HPA axis can be activated by treatment with hypophysiotr ophic factors or moderate stress throughout gestation. This review foc uses on the development of neuroendocrine mechanisms controlling HPA f unction during fetal life.