Fetal hypothalamus-pituitary-adrenal axis on the road to parturition

1. Activity of the fetal hypothalamus-pituitary-adrenal (HPA) axis waxes an d wanes as a function of gestational age. 2, In a number of species, including sheep, at the end of gestation there i s an increase in HPA activity, as characterized by an increase in fetal pla sma glucocorticoids, 3, To a certain degree, the hypothalamus, pituitary and adrenal all act aut onomously and, therefore, may be thought of as contributing to the initiati on of the signal that results in the increase in steroidogenesis before bir th. 4. Because it integrates sensory information from beyond as well as within the HPA axis and likely triggers developmental changes within the pituitary , the hypothalamus may be a 'first among equals' in being the ultimate sour ce of triggering information for the HPA axis.