Third trimester - the newly constituted transitional zone (TZ, medium grey) acquires the enzyme 3ß-HSD while the expression of P450C17 remains, thus allowing the production of fetal cortisol. Second trimester - chromaffin cells (CC, darkest grey) originating from the neural crests migrate through the fetal cortex to progressively colonize the center of the gland to form the future medulla (Med). Fetal zone (FZ) - expressing the P450C17 cytochrome, is responsible for massive secretion of DHEA and DHEA/S, used by the placenta as estrogen precursors. During the first trimester, the fetal gland is composed of a definitive zone (DZ, light grey) and a fetal zone (FZ, darker grey). This schematic representation is divided into portions showing the fetal adrenal gland (right) at the first, second and third trimesters of pregnancy, and the adult adrenal gland (left).
Ontogenesis of steroidogenic enzymes in the human fetal adrenal gland. New data suggest that the principal androgen made by the human adrenal is 11-ketotestosterone (11-KT), a rarely studied steroid. This chapter reviews AA biosynthesis, regulation, physiology and biological action.
Girls, women, and prepubertal boys may be negatively affected by AA hypersecretion in contrast to adult men. Although adrenal androgens do not appear to play a major role in the fully androgenized adult man, they seem to play a role in the adult woman and in both sexes before puberty. The production of T by the adrenal glands is minimal ( 7). Although these steroids have little androgenic activity, they provide a pool of circulating precursors for peripheral conversion to more potent androgens (e.g.
DHEA and DHEAS are secreted in greater quantities than the other adrenal androgens. They include dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androstenedione (A4), androstenediol (Α5) and 11β-hydroxyandrostenedione (11βOHA4) ( 1). Adrenal androgens (AAs), normally secreted by the fetal adrenal zone and the zona reticularis of the adrenal cortex, are steroid hormones with weak androgenic activity.
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