The human fetal adrenal: making adrenal androgens for placental estrogens.

During most of gestation, the fetal adrenal gland is almost solely dedicated to the production of dehydroepiandrosterone sulfate (DHEA-S). This specialized ability of the fetal adrenal is unique to primates and occurs because of a specialized fetal zone that composes the bulk of the fetal adrenal gland. Morphologically and physiologically, the human fetal adrenal (HFA) glands are remarkable organs. The glands at term are almost the size of the fetal kidney due in large part to the presence of the fetal zone, which at term produces more steroid than is normally secreted by adrenal glands of the adult. Much of the steroid released by the fetal zone is DHEA-S, which is used by the placenta to produce estrogens. Herein, we review the features of the HFA gland, including its impressive ability to synthesize large amounts of adrenal androgens for use by the placenta to produce estrogens.